Which brings us to the bigger question: What's in it for users? Will the demand actually materialize? As noted, femtocells basically let users (whether consumers or enterprises) purchase on-site voice-and-data wireless connectivity as a service from carries. But one could do the same thing with, say, a managed-WiFi service -- or just skip the management and deploy WiFi (which is what most organizations do today). With VoIP, you've got access to a converged local network -- no carrier needed.

But that misses an important point: Femtocells also lay the groundwork for fixed-mobile convergence, since wireless devices can travel offsite while remaining on the same network — so there's no service interruption during a call when you leave the LAN. (You can get almost the same effect with a multimode device that does VoIP on the LAN, and cellular on the WAN, but you have to hang up and redial). How much that seamlessness matters to users remains to be seen — but if it's a lot, look for femtocells to really take off.