I've noticed the problem with fouls in the full game as well. I'm one of those people who absolutely loved the fouls in the demo. It was one of the major features for me since these kinds of fouls are necessary to have a proper representation of physical play in the game.
In the demo it was possible to coax the opponent into fouling you by shielding the ball and it was also possible to stop a counter-attack with a smartly timed foul. In addition it made tackling an expert exercise as wrong timing would result in either losing the player or fouling him. It took a lot of practice to get this right. In all, this contributed to a fantastic midfield game, the best I've seen in any game
Now in the full game, the fouls are back to the usual PES 2010 style + penalties. You're only likely to get a foul with a sliding tackle and then there is also a chance of a booking.
The big problem, is that in order to reduce the number of fouls Konami heavily toned down physical play. Players no longer connect as strongly when tussling for the ball and when pressing "pass button plus direction away from your goal" to get your player to strongly pressure the opponent he just hangs back indecisively. I've seen players actually stop shortly before reaching an opponent to avoid colliding with them. As a result midfield play has disappeared and the action has once again moved outside the two boxes as in PES 2010.
I think this an overreaction on Konami's part to complains by demo players that they were getting fouled far too often.
Imho the demo fouling system was just perfect. What needed changing were the replays after each minor foul which were unnecessary (and have been removed in the full game) and the advantage rule which needed to be implemented.
If there are others who agree with me on this I propose we send an email to Konami objecting to this change. My understanding is that the toning down of physical play was jury rigged due to time constraints and thus easily fixable in a patch, if only Konami sees that the fans want it back. It's a slim chance they will listen but it's worth a shot. Otherwise PES 2011 will represent not only a major step forward in the series, but also a lost opportunity.