posted on Jan, 26 2010 @ 04:40 AM
It's another bit of data. We know that TPTB are datamining Facebook, MySpace, Usenet, Forums etc, cross-referencing with other databases (government,
credit, etc). Every extra bit of information you provide helps this datamining process by increasing the reliability of links between one dataset and
another.
For all I know, Facebook is being genuine about why it's doing this. But giving up any item of data about yourself is dangerous.