Try to update your profile on facebook, or write a comment and you will see in realtime the ads changing according to the content of the message you just posted.
About 3 years ago i had this idea (and actually also realized a prototype – it still live on my website) then spoke about it while being interviewed by google and they said that this was ad spamming!!!!
How about now that facebook is doing it? Is it now cool?
Just wondering if that googler is now working for facebook 
This link proves what i just said (even though it is a slightly different version of the original one, but the concept and technology is still there and it is very clear):
real time contextual targeting
Feel free to try
