Seems way too confusing. Target audience upon hearing the domain would probably go to 3Gnet.com instead, or try 3G.net.com or some other combination. Plus I've always thought all 3G names were very weak to begin with. What end user is going to know to type 3G?
It's also possible I'm just not clued in on what this is supposed to mean, and maybe there's an army of 3Gheads looking for this kind of stuff. Seems doubtful though.