The online poker sites have software that does its best to prevent bots from playing.
It's pretty much impossible to prevent unless you can algorithmically detect computer style play.
Which is a part of what those algorithms do, try to detect patterns that would indicate a non-human decision maker.
Obviously, as the AIs become more sophisticated, so must the detection algorithms. However, if the algorithm's play becomes so human-like that it defeats all attempts to distinguish it from that of an actual human (essentially passing the Turing test), would it still have an advantage over a human?
It is similar to the situation that we have in chess. Current algorithms running on consumer level hardware can consistently defeat even the best human players, and still online tournaments are being played. Of course, poker is played for money, so the incentive to cheat will be higher.