Facebook is doing the right thing by diversifying their portfolio. They've seen how quickly a social network can dry up and are wisely using their capital to avoid ending up like myspace.

If you really think about it there's not much more they can do with their original platform without upsetting some of their users. It makes much more sense for them to overpay for a product with traction than to try and spin something off of their original brand (last time they tried it with the Facebook phone it was a total flop).