To re-implement file transfer, we decided to hijack Facebook's speedy chat service to do our own packet transmission. This is the way it works:
-A python localhost server converts binary data into base64 ASCII and forms packets with uuid's, timestamps, seqnums, and the whole 9 yards.
-These packets get pumped over localhost to a user script (aka a Greasemonkey script) running on Facebook.com.
-This user script handles the scrubbing of incoming chat messages (packets) and populating the chatbox with outgoing packets.
-Facebook does _not_ make sending a chat message easy with custom JS, so in order to actually send a chat message, we signal the python localhost server to run a bash script that tells applescript to emulate a keydown event. Hacked up, I know, but it works! Also, this works for any application (desktop, flash embedded, etc) because it's as legit as a real keypress.
Just pumping the packets was the first challenge which we finished around 2am. The second obstacle was that facebook decides to drop about 50% of our packets after the first 15, so we then implemented a crude TCP style acknowledgement/handshake method that ensures each packet gets delivered. Implementing TCP inside of TCP... as meta as you get.
If you want to watch a video of a nyan cat GIF transmission, go here:
http://www.youtube.com/watch?feature=player_detailpage&v=tk5m0mqsrFs#t=74s
The main point is that despite even the most extreme legal restrictions on the internet, the next generation will always find a way :D
Github: https://github.com/pcottle/emotiface
Happy to answer any questions. Techcrunch also showed up and filmed / walked around the office (which was surprising considering the relationship between the two). I remember the techcrunch guy specifically saying "I feel like I'm at the Deathstar" when he walked through Facebook's double doors.