I definitely don't mind journal posts about "hey guys, I've entered this contest, if you like my entry, please vote for it" but I dislike people who comment on my deviations saying "very cool pict, hey can you vote for my...?"
I think it's fine. basically, if they say "Hey I'm entering this contest. I'd love it if you'd check out my entry and vote" or something along those lines I have no problem with it. But if it's more like "HEY EVERYBODY VOTE FOR ME CUZ IM AWESOME AND U ALL LOVE ME" then it's just obnoxious
I think as long as they aren't being pushy and they are asking nicely and asking ONLY their followers, then it's fine. but going to random people begging them to vote, that's just rude. (i've had it happen to me many times)