Perhaps this pretty graphic is true for at most 15% of the 30000 people laid off from Bear Stearns and Lehman but it's certainly not true for the all 30000 people who were working at those banks because the headcount at the remaining banks has not risen accordingly. It's entirely possible that not everyone on the planet has a LinkedIn profile.
It's also likely that the "best" people at these companies (in terms of staying on top of their career, keeping contacts, etc.) are the ones using LinkedIn.
Unlikely, from my experience people back office/middle office people are far more likely to use it than front office people. Which probably skews the data a lot. FO people are much more likely to use Reuters instant messaging or Bloomberg to keep in-touch, etc.
