Someone should make one of these that runs in your browser, where you literally just click "Share" and it shares you screen and gives you a link to stream it to other people. As in, no screensharing client to run/install, just click Share and go.

I'm not sure about Flex, but it can be done in Silverlight 5 with P/Invoke, and with Silverlight 4 with Elevated Trust and you'd have to actually install it (Although it can be installed with a single click of a button)