The Facebook platform that I talked about a week ago is already demonstrating how incredibly powerful distribution through friends can be, when it's well executed. The most popular Facebook app, iLike, is rapidly beating speed records for application growth, signing up
25%more than 10% of all Facebook users in two weeks.
This led to desperate email like this from iLikes CEO to...basically everybody (one wonders: Would he have gotten faster help on Facebook).
Vis a vis my comparison of Ning and the Facebook platform - Marc Andreesen now has a blog and did a thorough blog post on this problem and the Facebook platform in general. What he's saying about the death from success scenario is that, far from shifting control to humble developers, the size of Facebook means that you either need to be big already or have venture capital to use the Facebook platform - if you're going for success that is.
There's a couple of strategies to survive of course. Charge users - or limit your distribution to some identifiable subset of Facebook at first (a specific network). I'm unsure how you can make it polite to be invitation only on Facebook - since gifting is so much part of social network friendliness - but possibly you could do a cheap-to-serve static app for everybody and the rich experience for paying/selected customers.