I'm always suspicious of polls which require an email address. It could be a marketing gimmick, or perhaps they will in the future want to know what people at FR and DU think (based on the URL from which they were referred) on a particular issue, and email polls to a 'test group.' If they are going for uniqueness (avoiding multiple voting) they could use IP address more effectively (most people have more email addresses than they have IP addresses). Maybe I'm just paranoid:)
I'm always suspicious of polls which require an email address.
That's where my Yahoo account comes in handy, I rarely check it.