Exactly. I'm surprised this didn't come up more in the comments and that even Joel Spolsky, when commenting himself, didn't mention it. He was not saying that StackOverflow is in a similar situation as Starbucks', just that Starbucks was one of these cases where it makes sense to take VC money.
"There are a few indicators for the type of company that I believe can benefit from, and should take, VC."
Which means, the list in his article of companies that can benefit is more academical, and each of these may not apply to StackOverflow.
The response from 37signals is a bit presumptuous in the sense that it assumes Joel means //all// of these apply to StackOverflow.