[cos]

"performing" in what sense?

If someone joins a group, for example, I'm much less likely to see that, whereas before I might've looked at the group based on the title. If someone adds a friend who I know, I probably won't notice now, whereas before I might've seen it and added that friend. These kinds of things are valuable for social networking.

What kind of performance are you measuring, and why does it matter more than other kinds?

[blader]

I was speaking as a Facebook application developer responding to the comment about "applications can no longer be viral". I have no idea whether it's working out for Facebook as a whole, but for our own purposes it's looking very good across a whole range of metrics, mostly growth (user acquisition and activation).

As a data point, these guys: http://apps.facebook.com/livingsocial managed to get around 2 million uniques over the past couple of days, mostly from Feed virality. Again I have no idea if it's good for Facebook as a whole (and the only people who can say for sure are people with access to that data at Facebook), but for application developers it's been great.