Comment It's for Rendezvous support more than anything. (Score 1) 101
While I'm sure that many of the reasons outlined here about why you could use this are true. I think Apple is doing this for Rendezvous support. The Zeroconf guy has basically said so. I know there was an article where they said they (Apple) wanted to use IP for just about every connection instead of inventing new protocols. Rendezvous is not just for iChat, but is for other devices and technologies down the road. This fits in to the big picture.
Of course if THAT'S true then we can start speculating about what "device" they're coming out with that needs IPoFW.
Cheers,
John