I think the biggest problem with this view is that it assumes users will stick around if things stay the same. Twitter may be growing at impressive rates right

I think the biggest problem with this view is that it assumes users will stick around if things stay the same. Twitter may be growing at impressive rates right now, but will that continue, and will the users actually continue using the service? I simply can't see the majority of these users sticking around without there being more to it, in the form of value-added services. In addition, there are many cases of the "grow the platform" idea failing: Myspace and Youtube are damn good ones. Yes, they both have lots and lots of users, but where are they in terms of profit? Last I heard, they're both operating at a significant loss, although I haven't seen numbers for Myspace in a while.