Since there were bots the poker sites have started detecting bots. If a player played every day exactly 800 tables (or exactly e.g. 8 hours), it would be instantly banned for being a bot.

Bots have a lot of randomization now to make it appear human: sleep randomly to emulate "thinking", click on different parts of the button, randomly move the cursor around but still humanly, click next to the button, move the cursor on one button before moving it to another button to actually click, and so on...

I pointed this out to a guy I used to work with when he was creating a bot. I correctly guessed he'd not allowed for the fact someone might spot a player with sub 1 sec response times who always clicked on the exact same pixel etc. He added some random waits in here and then, every now and then you'd hear a flushing sound from his computer as his bot 'went to the toilet'.

Sites try, but can fail.

My favorite story was someone playing 120 tables simultaneously, who was verified to be human. See http://news.ycombinator.com/item?id=1899310 for discussion on that one.

Well I think that depends on the poker provider. Titan-Poker didn't.