Okay, this has got to be the most sinister thing of all. Most of these fake-follower websites don't require a Twitter password to buy followers for an account (and who would give their password to a sketchy website like that anyway?), so you don't need to be the operator of an account to buy fake followers for it. Want to make Mitt Romney look bad? Buy him really obviously fake followers and give them all the same profile picture.  Because Twitter is sometimes slow to close down fake accounts and buying followers is incredibly easy, this is a pretty effective strategy for messing with people. Best part? It's nearly untraceable, meaning that a suddenly and horribly popular account holder will be pounding his fists on his MacBook while you gleefully watch his real followers shake their heads at his lack of ethics.
Not that you should do this at all. Just saying it'd be really easy and really fun and you wouldn't get in trouble.