The problem with 3G video calling is that the networks don't fully support it.
If this was the case we'd be able to make a 3G video call whenever and wherever we like.
Take a look at any 3G coverage map and you'll see why. 3G blackspots abound.

I've said it time and time again, it wasn't just Nokia that ruined the N900's chances. The networks did the most damage IMO. T-Mobile, Orange and 3 refused to stock the phone because they couldn't fill it with their restrictive branding and WAP only services and apps. And their refusal to invest in their networks is evident in the fact that they are all now bringing in restrictions and caps on the internet services.

To make a 3G video call, both handsets have to be within a 3G area with a good strong signal, no blackspots and no dropouts. That just doesn't work in the real world. Not even on the iPhone, Android, WP7, Symbian or WebOS.