Facebook has a clear monetization model. If Facebook releases a product like AdSense - which shows content relevant ads as well as targeted ads will be a great blow to Google.

Also, as far as mobile is concerned there are apps like Karma (http://getkarma.com) and TagTile that Facebook recently acquired - and they showed a great way to monetize using Facebook data.

There are some many apps that have crossed millions of users just because of Facebook integration.

Haters gonna hate but Facebook is here to stay for a long, long time.