They did. The argument was that this fraud was going to occur at the highest stakes games, so that it was worth it. So if you weren't playing those...

Edit to answer the original question: Yes, it's a potential advantage, but not as much as you think. In Holdem, the most commonly played poker game these days, you only get to see two more cards per player. How it was typically done is two players would put the victim "in the middle", surrounding them with raises. One colluding player would stay in with a weak hand, and force the victim to put extra bets in. It's actually fairly difficult to get any kind of advantage in poker, and that includes from collusion. Most people who get extra advantage from collusion do it by playing soft against each other, as using it to optimize your strategy against others requires a high degree of skill -- enough skill that they can probably beat the game without colluding. Good players will catch on quickly, and then nobody will play with them. The poker world kind of polices itself, and cheaters and deadbeats get reputations quickly.

Now, if you know your *opponent's* cards, then that is a HUGE advantage. There was a case where a software developer put a back door into the poker software so his confederates could see all the cards, including their opponents. But they were caught fairly quickly because their results were so outlandish it was obvious something was going on. Occasionally in a live game, you can sit next to a player who is not protecting their hand and you get to see their hole cards. Since you can play perfectly against them, it doesn't take long to get their money.

The other thing is, you can spot colluding players pretty easily if you know what to look for. Signaling and collusion happens in live games, too. It's like the old saying about if you can't spot the fish, then you are the fish. Those things are concerns, but the games were very good.