I saw this guy that made a killing on Poker-room back in the days before dubya signed the Ports Act. Can't remember his nick, but his bots would play 1-2 limit, and absolutely kill it. He would play 8 tables at a time for about 12 hours a day. Each table would consistently be up about $150 each by the end of the day ($1,200 per day!).
I'm almost certain they were bots, because they would take exactly the same amount of time to make a decision to call, raise or fold. I got involved in a bunch of "test" hands with the bots, just to see what it would do. It almost always made the mathmatically correct decision, based on pot odds and odds of winning.
I used to play up to 4 tables at a time - there's no way a human could play 8 tables and take exactly the same amount of time (it was about 3 seconds) on every table!