Theres a lot of available APIs on infochimps. One possibility is
their IP demo API -- http://www.infochimps.com/datasets/digital-element-ip-intelligence-demographics
their geo API stuff -- http://www.infochimps.com/apis/geo
Also another data provider like Rapleaf can help get a lot of info from just an email address. Send them the email over the API and return as much profile info as they have on the individual.
If you can get them to give up google credentials or linkedin, then you can access contacts, etc.
