StackOverflow was successfully expanding their service even before this purchase. I'd imagine stackoverflow jobs is a valuable area - sure it's not linkedin but it's still really good. SO also has really strong community following so there's always room for easy expanding.

It's not about the QA area but other areas that surround it. There are a lot of ways to integrate products to QA part of the web - you already see "Python jobs" on python questions which I'd imagine should work really well!