It’s a question that can be addressed from two directions, both interesting. You can frame the question as, “What is the business model?”, or you can ask “How does a community support a resource it finds useful?”.
I find that this is a question that your average user doesn’t really consider. I think that’s just common human nature—if there is no cost of entry, we don’t think about the costs of upkeep.
An example: Your average churchgoer might never think of what it takes, financially speaking, to run a church if we didn’t pass an offering plate every Sunday—but the costs are there regardless.
While you can “pass the hat” in meatspace, it’s much harder online. I’ve got a fair amount of experience with this, as I largely finance a community-run Web service. There are many generous folks who donate to help us stay up and running, and I greatly appreciate those people—and they know who they are, so I don’t need to name them. But I’m always bemused when people think that a service package like what we provide with the RMFO network doesn’t cost that much. I wish that it didn’t!
If you read Kellan’s piece, you’ll run across the same words I did:
A few years ago this would have been an unprecedentedly large amount. The idea that we were all going to get rich selling online services was so firmly rejected that it became a commonly accepted truism that “people won’t pay for things online”, and yet, quietly, almost under the radar this seems to be changing.
It really is. I think this is the maturation of the Internet population understanding, fully, TNSTAAFL.