DW's Wall Street I-bank employer has been hiring like crazy lately (they were mentioned in the OP's article). She's in the back office, not on Wall Street (or anywhere near New York for that matter). DW has roughly doubled the headcount in her group because they are so extremely busy right now.
They recently had a "densification" of their building. A building designed to hold 1000 now holds 1800. Yes, everyone is sharing a cube now. The company tried to send overseas some of their IT support services to a Latin American country, and that failed, so the IT support folks are now based in her office too. They have been hiring a lot of IT development folks too down here. Business is booming!
Where are the customers? Trading and investment banking is always going to be needed. A few places went up in smoke, they got some business from those guys. A few others don't have sterling reputations any more, so there's some more biz. Believe it or not, we are experiencing economic expansion and along with that comes trading activity, M&A, underwriting, etc.