This is no biggie at all - after all that value is customizable.
Just a heads up that the default value, "*-jabber-*", doesn't work very well with iswitchb-buffer which works by matching substrings. Since "*-jabber-" is a substring of all buffer names created by emacs-jabber, you have to use something like "ber-*" which is slightly awkward to type. If the name would be something like "*-jabber-roster-*" then I could get there by typing "roster" or, more often than not, just "ros".
Again, easy enough to customize but I think that changing the default would make emacs-jabber a tiny little bit better out of the box.