I think that if we want one user - one vote, the IP-vote coupling is flawed as design, especially nowadays when ISP's rotate IP-adresses.

Better link the vote to user id directly.

Of course this pre-empts Anonymous Monks to participate in polls, but then who wants statistics more twisted than necessary, ;-)

Update:
Something is rotten in Denmark and it's not the surströmming which is a purely Swedish phenomenon.

I just tested voting on an old poll, "My age is", which I have never voted on before and got the dreaded message "You have already voted from that IP (62.20.xxx.yyy)"

This I find odd unless the voter-table only get reset when a new poll is out.