i have a p4000... it's my first pda/ ppc. being new to this whole affair, it took me hours of online research to understand which names are pertain to this device, and to separate many other names that are similar htc products, but *not* this device.
just for fun, i'll add to list.
i've also seen sprint refer to it as the Sprint Audiovox PPC-6800.
and i understand that verizon will be calling it the Verizon XV6800.
i'm also pretty sure that i saw some adverts from htc *themselves* calling it the mogul (and the pictures did not have any carrier-specific branding on the casing).
and i've also seen people getting scolded in forums for asking about the titan, and being told that there is no such a device... confusion created, of course, because of the similarly named HTC TyTn.