Maybe also explain why would someone buy Stackoverflow votes...
Stackoverflow accounts are often asked for at job interviews, or a nice addition to your CV, if you're a programmer.
If you buy these votes i guess you could inflate your account points and thus make it look like you know a hell of a lot, while in reality you don't, or a lot less.
I don't think it's smart to buy this. If your answer is wrong and you buy upvotes, it just looks dumb to everyone else, and if you're giving right answers to questions, there's absolutely no need to buy upvotes.