Gee, I would say mostly a mix of Incase snap-on/Incipio Feather or a variation of those. Also, equivalent of the NGP type case or a simple gel case. Some Otterboxes, and a surprising increase of 'naked' phones.
This is in the Boston city area.
That is another trend I've noticed as well here in Chicago.
agreed. but i see a lot of speck cases as well. helps that they have a large presence in the apple stores so thats probably why. i've yet to see another BookBook and people ask me about it all the time.