Jun 09
The chance of someone be blocked by mistake in this screen is very high. Since the distance between the actions of Accept and Block has only a few pixels… a small slip with the mouse and you unintentionally will block someone.
Error prevention
Even better than good error messages is a careful design which prevents a problem from occurring in the first place. Either eliminate error-prone conditions or check for them and present users with a confirmation option before they commit to the action. (From Nielsen’s usability heuristics)