Although Vinge claims to have no idea, in Rainbows End obviously Rabbit is an AI, which though it didn't deliberately harm our heroes in the story is obviously an immediate danger to all the survivors, it was attempting to purloin the YGBM weapon and even though that weapon isn't (apparently) exported in finished state, it would now be much easier to re-develop for all the involved parties - which is bad news even if Rabbit doesn't have it.
It's pretty obvious what the catastrophe is in the Zones of Thought novels, and for Tatja Grimm well, to the extent Tatja herself isn't a catastrophe (she starts a major war just to get what she wants!) the whole reason Tatja is so different certainly counts.
I don't know about The Peace War though, haven't read those.