[Eru]

If you abuse it it might be, but I don't think they care much unless people start to complain about it. More specifically, if people who are paying the site start to complain or decide to stop paying. ;P Top sites do what they do because of the advertising revenue and membership fees.

Also, we're not technically buying votes since you can type .vote and get the 1000 gold, then not vote if you don't want to. If you only got the reward after the vote, then it would be more dubious.