[juanojeda]

All of those things are fairly trivial for FB to track. Age (obvious), Location (trackable through Places, geolocation, etc. through that thing in your pocket), Gender (presumably you would post a status update about something that big?), Employment (status, amassing colleagues as 'friends'?). It seems like they've hit on a constantly self-updating demographic info machine...

[pork]

I was referring to your mention of "permanently backed up", i.e., stale demographic information, whose value decreases predictably with time. While FB is in business, you're spot on.