There is a good blog by Tom Keating on TMCnet about the challenges faced by WebRTC. The article can be summarized to:
1. It is still early days for WebRTC, “The various browser implementations of the current WebRTC specifications are the first go around with some of the implementations not even complete”
2. The codec issue, is it going to be H264 or VP8?
3. What are MS going to do with CU-RTC-Web?
I believe that the first issue will only last for 2013. By this time next year we’ll have robust implementations in Chrome, Firefox and Opera. The second issue will be solved by companies like us if the browser vendors can’t agree. The codec debate will continue though, but perhaps Google have an ace up their sleeve with VP9. If they can show that it is roughly as good as H.265, then perhaps its royalty free status will get the nay sayers on their side.
Full article here: http://blog.tmcnet.com/blog/tom-keating/webrtc/webrtc-challenges.asp