"When/if the network security team figures this out and 
    blocks it, I'll demonstrate a few other ways in which data 
    can be exfiltrated."

I loved this line.

He mentions blocking there, but given the technique, could forensics show that this has been used? For example, could some future whistleblower for a national security agency (ours or anyone else's for that matter) use this to exfiltrate files without risk of discovery after the fact?

Could an organization like wikileaks or the guardian use this as a technique for whistleblowers to leak files safely?