Let me suggest we might call them "tool" or "service" businesses. I think this is a useful distinction, but it's also one that breaks down at a point. Reddit,

Let me suggest we might call them "tool" or "service" businesses. I think this is a useful distinction, but it's also one that breaks down at a point. Reddit, for example, was a useful way to kill time even before it had a big user community, just because it had a few good posts each day. If kn0thing and spez sent you that list by email rather than maintaining it on the web, it wouldn't feel like a community but like a service. Finding a service that can be delivered usefully without a big community, but can also become an identifying activity for a growing community, seems to be the secret sauce of many successful community sites.