One of the least-understood developments of the last few years is the growth of databases of personal information linked to email addresses. Rapleaf is probably the leader in this field, but even Flickr lets companies search their API for users based on an email address. I wrote a service that queries all the data sources I could find to demonstrate how much is out there:
http://web.mailana.com/labs/findbyemail/
Give it a try for yourself, you might be surprised by how much companies can discover about you once they know your email address! Many services give out at least your full name and a location, which is often enough to get your address and a phone number from a service like whitepages.com.
Pete Warden's blog 