Who told you that when you chat with someone on Omegle or Chatroulette and hide your face you will be anonymous ? well think again, I developed my own Chatroulette website and the first problem I had is the heavy load of video/audio streaming, so I had to a P2P solution which connect the users directly to each other and start streaming video/audio.
appearntly Omegle and chatroulette are using the same method so anyone who can see you on cam can also get your IP.
the simple example of a map generated using these data automatically is http://www.chatroulettemap.com/
what can anybody do with your IP address ?
by using web proxy you are still not fully anonymous the only secured way is VPN.
Have fun but stay secured, enjoy