To be fair, this is probably the only time I've seen the term hacked used correctly. I no longer know whether I should use it in this sense or the "incorrect but used by almost everyone" sense.
I don't think it's used correctly here. They didn't hack together any code, they didn't hack on some multipart kludge. All they did was break rules by buying votes.
"Gamed" should be the word.
Haven't you heard? Marketers call marketing tricks "hacking" now. o_o