Another aspect that isn't mentioned here is this. Over the past 7 or 8 years Bay area companies have had to keep gradually increasing their employee's salaries to accommodate for the rising real estate profits, which has caused competing companies to have to do the same and so on.
We've finally hit a point where companies are now realizing it isn't profitable to continue paying employees higher salaries and are letting folks go, and those folks are moving to more affordable areas in the country.
True but not just an app. The underlying success is that they have successfully mixed 4 existing services into 1
1) Facebook
2) Twitter
3) foursquare
4) photos
Who in their right mind would work with this funky company in the first place? They seem to be hiring morons. Or maybe they have the Superbowl models doing their Security.