I think one of the biggest challenges to videophone's remains the lack of interoperability between them and their software. I mean, here you have Jeff with his new toy. I have a Packet 8 videophone, software from XTEN, Sightspeed, Yahoo, the last three of which are SIP standard all the way down the line, and yet the ability to be interoperable is not yet there. Motorola is sending me not one, but two Ojo's so I can have someone to look at. Maybe the company's product that Jeff has on his desk is a first and proper step in that direction for the mass market.
Right now depending who I want to chat with, determines which piece of software has to be used (or in some cases hardware). If email worked this way, it would be like AOL was until the mid-90's. They had lots of users, but no one could email to anyone on AOL from the outside or vice versa. That model eventually eroded and like the wall in Berlin, it eventually fell creating a whole new economy.
Pal Erik Lagerway at SipThat regularly stands on his head about following Open Standards. If e-mail's POP3 and SMTP standards aren't good enough as indicators for where Video and Voice need to go, then nothing is.