This system collects your name, your key and your vote. Names and keys are collected to uniquely identify avatars and are not used for any other purpose (though you should be aware that anyone who can get within 96m of you, or any object you own, in Second Life, can get both your name and your key - this is not secret data). The only other use that I would put keys to is to send a warning to everyone if, somehow, I discovered that there was some fatal flaw in the HUD tagging device which caused your computer to explode or some such.
Your votes will not be used for any untoward purposes either, just to produce the tables on this site. All data will remain anonymous. Nobody using these pages will ever be able to tie you to voting for a particular sim.