Skype one-to-one is peer-to-peer. Your video data goes straight to the other person. Skype group video chat is run through their servers. The aggregate the vid

Skype one-to-one is peer-to-peer. Your video data goes straight to the other person. Skype group video chat is run through their servers. The aggregate the video sources on their side and send those back out to each participant. So, there's an inherent cost of that much data (n*(n-1), I believe) and the server itself that Skype needs to pay for. Audio group chat is easier because the resulting audio streams can be overlaid on top of each other for everyone in the same group. So, if 3 people are talking in a 10 person chat, it's 3 inbound streams and just 10 outbound streams, not 30 outbound. Video can't be overlaid like that (at least not without it looking weird :P)