Note: A friend just pointed out the explanation for this behaviour on Tetris Battle's help area which is helpful to understand what may have happened:<p>All of the games with a Facebook name and profile picture are real game plays from the actual player. If the server is unable to find a player, then the title AI will appear on the opponent’s name to tell you that it is an AI bot playing against you.<p>I should note - that in my screen shot, there is no indication of it being a replay though.
A friend of mine tried to do a statistics project on the algorithm. Made the interesting discovery that the blocks are randomized within 7-piece sets, with the system going through each different tetramino before repeating any one.
In the first Block Battle thread, someone noted[1] that the individual matches are often just replays of past games. At the higher levels (around 20+) you can actually randomly play against the AI, but this is at least a little more honest, as its name is A.I., and it goes <i>very</i> fast.<p>[1] <a href="http://news.ycombinator.com/item?id=2389740" rel="nofollow">http://news.ycombinator.com/item?id=2389740</a>