This technique consisted of 50-70 people who used this technique. They actually used this primarily in Ohio casinos even though most of the criminal group where from New York City. In this case I think the downfall of this was that there were just far too many people doing it and that itself made it much more likely for them to solve the crime.
So basically how it worked was a player would enter the game and usually buy one hundred yellow $1 chips. As they played they would secretly pocket as many chips as they could. Now they would leave the table and hand off these chips to another member of the crew. This member then would proceed to buy in for $200 and the player would specifically ask for the yellow chips.
The dealer would then proceed to give the 40 $5 chips, and then they would mix the chips their friend gave them previously into the game. Now their $1 chips are now worth $5 and would pay 5 times the regular value if they won. Out of all scams that I have heard of in casinos this one must be the most simple for anyone to pull off. I say it serves the casino right for being this gullible in the first place to even allow this to be pulled off in the first place.