Those are far-off examples. Granted, perhaps in some cases people should be prevented from doing something utterly stupid but that shouldn't keep us from exploring opportunities in general. Just because kids occasionally hurt themselves during play they shouldn't be forbidden to play.
Would you want to be able to change your brain so that you can productively work 70 hours per week? I wouldn't - it'd quickly become the standard against which you're measured, while the rewards for passing the test stay about the same.
There's a similar argument to be made for being able to share your life on facebook - it displaces alternative interpersonal interactions, so you have the same amount of human connection except with your social graph sold to marketers.