afaik the upcoming version 1.9 hs this for sure.
but its only good if your users accept cookies. they can always remove the cookie or not accept it and vote again.
Also in TikiWiki 1.8 there is the CookieMonster problem. So it could be that the Tiki site is actually sending out the cookie, but the browsers limitation of 20, has been reached, therefor it gets disgarded straight away.
Project Admin Team