[freyr]

Further, consider this excerpt from http://en.wikipedia.org/wiki/OAuth:

A growing number of social networking services promote OAuth logins to the dominant social networks (Facebook, Twitter etc.) as the primary authentication method, over "traditional" email confirmation type processes. Users of such practices include Klout, Kred, Foursquare, and others. The permissions granted typically permit the authorized application to download the entire social data stream belonging to the user, which is stored for data-mining purposes by the application provider. By facilitating such use, OAuth is acting as a component in a social engineering type scam where users of the application probably do not realize the extent of the data they are sharing.