Super speed! Just think how much you'd have to spend on food.. never mind tearing up so many roads, shattering every window with the sonic boom as you go by.. it would really be an epic fail.

Great points!! I think this has also been addressed in the comics before so this may not be the case, but I always had this thought in my mind what if you were not personally experiencing "going fast" but rather everything seemed normal and everybody else was really slowed down. Like you run across the city, country, world, etc. but it's just like a normal person (other than your stamina doesn't give out, joints hold up, etc.) to yourself even though to others you seem super fast. If the powers worked like that, it always seemed like a horror to me! (I also hate running).

Very interesting way to consider, and I can definitely see that! I also think it might be like how Busiek depicted Samaritan in Astro City...you never really can "take a break" for the most part, how would you stop helping knowing you "could" just power through it and keep going?

I gave this a lot of thought once, and I concluded that almost every single comic-book superpower would either be useful in primarily unethical ways or would likely get you or someone else killed unless it was supplemented with an additional superpower. Flight? Beware of power lines, freezing, hitting a building, getting lost over the ocean, being shot down by a hunter or foreign power or scared gun owner. Super-strength? Be careful not to crush a loved one, bring your house down over your head. Super-speed? Hope there are no obstacles or tripping hazards. Walking up walls? Not gonna help if you fall off the wall. Invisibility? Read some H. G. Wells, that's going to end in disaster; even if you can turn it off at will you're susceptible to all sorts of severe injuries accidentally inflicted by people who can't see you. Intangibility? What if you sink into the ground, or re-materialize around airborne contaminants?

Healing powers, now those would be nice to have, but that's entirely self-centered.

MWGallaher - interesting observation on single powers!

It gave me pause for thought because I agree with those perils you mentioned. Invulnerability was an exception that came to mind potentially.

But for a fun thought exercise, I thought I would use my beloved Legion of Super-Heroes and see how their powers might stack up with that consideration in mind:

Cosmic Boy - magnetism, seems useful to me. Grab guns away, lift a car, etc. Could still be dangerous, but not as inherently perhaps as more directly destructive energy based powers.
Saturn Girl - aforementioned telepath issue, all depends if you can shut it off
Lightning Lad - electrical powers, feels like we are straying into potentially destructive risk again
Triplicate Girl - not sure as a power, would be fun to mess with people at the office though
Phantom Girl - risks around phasing back in (e.g., solid surfaces)
Chameleon Boy - used for honorable purposes (so we're going to assume these are all noble hypotheticals), this seems useful and lower burden. Case of "mistaken identity" in criminal type situation could backfire maybe.
Colossal Boy - yeah...one "bad step" is all it would take
Invisible Kid - as pointed out, invisibility would definitely have major risks
Star Boy ("make things heavy" power) - heck, he accidently killed someone in the comic with this and was expelled for a period!
Brainiac 5 - super computer smart, high intelligence does not always make life easy and this is at a whole other level, but direct physical danger seems low
Sun Boy - energy based destructive risk again
Shrinking Violet - one "bad step" again, but coming the other way
Bouncing Boy - other than knocking stuff all over the place like a cat at 3 in the morning, I don't see the issue
Ultra Boy - In addition the Superman like burden mentioned earlier, having to switch them on and off one at a time feels like a timebomb waiting to backfire on you (like switching to invulnerability a micro second too late!).
Mon-El - Superman type burden again
Matter-Eater Lad - I want to give a serious answer, and I know this is all make believe...but HOW WOULD THIS EVEN WORK???
Light Lass - Little Billy accidently floats away forever...
Dream Girl - knowing the future would drive one mad quickly I think
Ferro Lad - Fairly invulnerable, risks around strength level potentially.
Karate Kid - not a meta human.
Princess Projectra - somewhat like shapeshifting, used for honorable purposes might be very effective and lower burden.
Chemical King - controlling chemical reactions feels high risk if something goes wrong
Timber Wolf - enhanced agility strength, I feel like this could be a little more practical category for the real world (I think of Captain America in this regard as well). Not nearly the level of risk of Superman having to hold back, but enough of an extra edge to fight crime potentially.

I'll cut it off there even though there are many more characters, but it feels like that further supports (to me at least) that yes, many powers really would be hard to manage in a real world setting.

Oh, the Legion are the ideal test subjects for this thought experiment!
Triplicate Girl - I assume there are some convenient definitions of how her power works, but before accepting it in real life, I'd want to know what happens if one body is injured when you reunite? If the composite body is restored to health, that would be a separate power from triplicating. If injuries are retained, that triples the risk to the whole. It's established that if one body dies, the remaining two can unite, but can two unite if all three are alive? If not, there's a risk that one body could be imprisoned, or lost, or comatose, forcing the others to live separately, which at the least would double the grocery bill.
Matter-Eater Lad - Grocery bills are of course no problem, but depending on "HOW WOULD THIS EVEN WORK???", the power might be a liability to the general public as a threat to the sanitation system!
Brainiac 5 - Agreed, that one probably wouldn't get you killed, and could potentially be financially beneficial via ethical applications, but getting too far beyond current genius levels could be just as maddening as Dream Girl's powers. I'd imagine a "12th Level Intelligence" would be capable of nearly identical prognostication, analyzing current states to predict outcomes of nearly everything, including your own actions. But assuming it's just being really smart about science and history and arts, I wouldn't be as scared of it as most other powers. I wouldn't volunteer for that kind of intellectual leap, though.
Chameleon Boy - Used judiciously, probably safe enough, but as I recall, he could also transform into very large or very small animals, risking the same consequences as Colossal Boy or Shrinking Violet face.
Princess Projectra - Agreed, safe if used wisely, and potentially financially beneficial in, say, a magic act.
Cosmic Boy - The danger here is the inability of a magnetic field to discriminate. While you're grabbing that gun away--which would imply a very strong magnetic field!--you're also yanking out medical implants from people's bodies, nails out of structures, and lots of easily-imagined magnetically-susceptible metals the displacement of which would be disastrous.
Saturn Girl - It's hard to think of an ethical application of that power. In criminal investigations, it could potentially reveal details that could be confirmed via hard evidence, identify witness, and clarify the timeline of events to refute defenses. But if you've got the wrong guy, mind-reading would be a gross personal violation, right?
Timber Wolf - He needs a combination of powers to be safe, I would think. Exercising the enhanced agility without the strength to weather things like landing impacts could be risky.
Invulnerability - Potentially extremely dangerous unless you can turn it off at will. Bummer about the appendicitis, man, but we can't get to it.

I think it's simple:

If it's Silver Age, things like that just don't happen and everything is la dee da simple.

If it's Bronze Age, Duo Damsel does have children, but conveniently it's twins and each personality is carrying one of them when they split apart and nothing inconvenient happens along the way and she eventually delivers both in her united form.

If it's Modern Age, one of Triad's selves is carrying a single baby but the other two aren't and they get into a whole conversation about how their individual rights are being robbed and how they should have the freedom to be their own people and not burdened. And they frown a lot and say snarky things and refuse to rejoin up and go off on their own talking about how they are FINALLY their own people now. Oh, and it's all told with bad art.

 Telepathy seems like it would be a real bitch to have.

On the flip side I think Mr Fantastic's power would be fairly handy