Just a quick drop-in (got some lawn to cut before I think about packing..heh) to say that all sorts of polls work just like this website. It registers your IP. Same way people here are pulling new anonymous IPs to bother us with new accounts once banned is the same way you can vote multiple times on that poll site.
Not technically difficult (you see the dolts here who figured it out) but not really worth it to boost numbers on a poll nobody cares about. As said, we all know who is #1. Priest Reunion tour (aka Ozzfest) had Slipknot. Not even main stage....