I've actually been wondering what the hell facebook has been doing with all of these engineers. Most of the changes I've seen on facebook have been pretty minor, no significant feature launches in the past couple years. I guess they do only have 1/10th as many employees as Google does, but it still doesn't make any sense to have a couple thousand engineers and no visible progress; I feel like they must have a lot going on internally that is unannounced. If we don't see any big moves by facebook in the next year (especially if Circles manages to have a successful public launch in the immediate future) I would be really surprised.