I once answered a question that asked how Stack Overflow makes money, but that was before the time of VC.
The Experts-Exchange team took the time to answer its own Q&A about its site (since it wasn't included in the roundup by Fortune magazine), and just about the only dig in there that halfway has merit is the business model dig:
We switched to a premium model to keep out of the Venture Capital business (been there, done that, got the t-shirt). Companies like StackExchange couldn't do it without the VC cookie jar. Where's the model? Huh, Spolsky? (I’m sorry. Did that slip out?)
It hurt, but I can't help but wonder if they're on to something. How would Stack Overflow Internet Services pay back the VCs? Ad revenue alone? There is only one 'paid' product, Stack Overflow careers, but it doesn't seem like that could sustain a business as large as Stack Overflow (Joel once mentioned on his blog that his jobs board brought in an extra million a year in revenue).
So what does Stack Overflow do when the VC cash runs out? Is this a get-big-and-take-the-company-public maneuver? Is that the only viable business model for Stack Exchange?
Edit: With the size of Stack Overflow's team, it isn't a stretch to say that payroll is at least $2 million a year, probably as much as 4 when you think about benefits (average 120K for a developer in New York City; x2 for benefits/taxes/all-that-other-good-stuff). Office space can't be cheap, so how long does $6 million last before you need another VC infusion?