Correct me if I'm wrong but from what I've been reading here on the forums, AT&T will not use wifi for voice (when they eventually release a wifi blackberry). If not for voice, then the only use would be for faster web browsing? If that's the case then I think it's pretty pointless to have a wifi bb on AT&T - at least till RIM updates the browser! I only have one bar of service at my house and I drop calls every once in a while. I don't guess a wifi bb would help that situation out as long as I'm still on AT&T right?
It means that on a BB that's attached to a BES (such as mine) it will have 2 or 3 browsers: a carrier internet browser that comes with the carrier's BIS service, the MDS/BES browser for intranet and internet if enabled, and a WAP browser from the carrier (called MediaNet on mine from AT&T). These are the browsers present on my BB.
Both of the carrier's browsers can be disabled from IT policy though, so they may not show up on the BB to the user. I think the comment was a little misleading because although these are "different" browsers, they are still the same BB browser but accessing different networks.