Yeah, that too! The problem is not capturing the streams because that can be done like you said with screen recording or even webcam recording, the most difficult part is injecting a stream as if it were your webcam and then synchronizing the streams so that when you're "nexted" you immediately find another chatroulette user so it seems transparent to the users being eavesdropped. Anyway, you're absolutely right, chatroulette is not private at all.

You might not be aware of this but any user can collect IP addresses and record ENTIRE video footage from random chatroulette users. I explained how in my blog http://fernandomagro.com/security/chatroulette-espionage/ . Anyway the concept is really simple because an attacker can open an even number of connections to chatroulette (2,4,6,etc) and then redirect the streams to each other. Say, I open connection1 and connection2 then I capture stream from connection2 and dump it as my primary webcam to connection1 and I capture connection1 and dump it as my secondary webcam to connection2. Only a tiny bit of linux hacking is needed.