I am certain that all the main sites are riddled with bots.
You will certainly meet people who multi-table maybe sometimes 10-14 tables which is tough to do. But on Full Tilt and Pokerstars you will regularly see "people" playing 23+ tables simultaneously ! Clearly not really humanly possible and a good poker player is unlikely to play that many tables.
The sites "claim" to monitor for the use of bots but frankly I don't think they are that active or effective. Check out WinHoldem.com | Win Holdem (http://www.winholdem.com) and you will read all about how these bots avoid detection from the monitoring sites.
The bots potentially have a great advantage over the average player. They can make very quick calculations, establish the % chances of cards winning/losing, pot odds
etc etc. They can monitor how other people play and overall just be good solid players. The bots can be programmed however u like and whilst it is true that some bots might be badly set up, you have to make the mental leap that if bots exist, then so do the parameters for a pretty much guaranteed solid profitable game.
The really really worrying thing with bots is that if you have more than one, and can get them on the same table then they can communicate with each other. They can share their hole cards and thus their calculations become even more accurate and effective.
Personally I think bots, plus the ease with which players can collude, plus the likelihood that there is some form of subtle and limited creative card dealing (to try and keep everyone happy and at the tables) is a key reason why poker rooms are no place for beginners. I have complained to both FT and PS about this.
There is one very simple way that the poker rooms can make the whole experience safe and fun for poker beginners and again I have made this suggestion to both sites. The answer is to introduce a set of tables that are SINGLE PLAY only. i.e you can only join the table if you are not sat at any other table. The poker sharks, the bot users and colluders will hate this as they get their $$ mostly from grinding away on loads of tables. They could sit at your single play table but I think they are very unlikely to. Its a simple solution to a big problem and I truly hope they take the idea up and soon!
I find the whole concept of sharks and bot users feeding on hapless beginners totally unfair and immoral and there is a desperate need to "clean up" online poker to make a secure and safe place . The existing micro tables don't do that because the sharks swim there all the time.
SINGLE TABLES are the way forward for all sites and should be a great advertising mechanism to bring in new players.
Watch this space ! :-)