I think he proves a very big bug in the entire ripple system.
If anyone can make those imaginary BTC or any other currency in the ripple system, and he sends that fake currency to alot of persons..
User 1, Fake bitcoin owner try to buy something paying with bitcoins in ripple, starts a topic or something, and send the fake BTC first.
User 2, receives the fake BTC and send the item who was selling (LTC, ripples, USD,etc) then he realizes that he cant trade his BTC anywhere, because its fake and get scammed.
This is not a bug. Users can trade this BTC to exactly the users who trusted TF who have not yet removed their credit limits to him. This is by design. TF might have just allowed 30-100 btc newbies to conduct real trade with eachother who might not have had any BTC to their name, based on TF's trust alone.
Now that seems to be a long shot, but that's the kind of long shot that Ripple at least makes possible.