Like many folks, I’ve been following the initial experiences with Facebook’s API; their first salvo in what appears to be a coming platform war.
From all appearances, Facebook has done a great job with the launch, but may have exposed to many to the seldom discussed limitations
of the infrastructure that powers internet applications. Marc Andreessen has an extensive analysis of the impact that pretty much hits it:

“… code that uses the Facebook APIs has to run on third-party servers — servers that you, as the developer provide. …”

“… when your application takes off on Facebook, you are very happy because you have lots of users, and you are very sad because your servers blow up. ”

“… unless you already have, or are prepared to quickly procure, a 100-500+ server infrastructure and everything associated with it — networking gear, storage gear, ISP interconnetions, monitoring systems, firewalls, load balancers, provisioning systems, etc. — and a killer operations team, launching a successful Facebook application may well be a self-defeating proposition.”

Marc’s goes on to talk about ILike, the first hit app on Facebook. ILike had to add more than 100 servers in the first week after their Facebook launch. Just a few weeks later, ILike now has more than 6 million users!

Of course, 3tera’s been talking about (and building for) this for two years. Had ILike been a utility computing user, the now infamous post begging for servers would never have happened.