It's very possible, actually. Just takes a lot of code, a knowledge of how http works, and a knowledge of what to do in certain situations ( if attack is BR then do this, if GS then do that, etc ).
I have the most popular comment on Cracked.com.
http://www.cracked.com/...-boo-redeemed-reality-tv/
Go down to the comments section, and click on the 'Votes' button, which will sort by votes. The first comment you see is the most popular comment on Cracked.com.
They validated the fact that you had already voted on a comment on the client-side, using javascript. So, I used an old version of mIRC to bash out a quick script that would just sit there and "click" on the up-vote button over and over again (bypassing the javascript). I did this, while at work, via the remote desktop app on my cell phone, connected to my laptop at home over a satellite uplink. About a half hour later, over 3000 up-votes. They fixed that little problem shortly afterwards. I rule.
P.S. The second most popular vote on Cracked.com?
http://www.cracked.com/...ns-criminally-insane.html
Made popular by yours truly.