James Grosjean showed up in disguise at the 13th International Conference on Gambling & Risk-Taking. He is one of the “advantage” gamblers that casinos usually expel from their premises if they are seen at blackjack tables.

Mr. Grosjean didn’t want to take any risk, that is why he wore a black wig and sunglasses to attend the conference held at Harrah’s Lake Tahoe. John Chang, also a skilled bettor, was one of the speakers who covered topics such as legal ways to beat the odds and online poker players.

Harrah’s spokesman, John Packer, said they weren’t worried about the presence of Grosjean and other gamblers whose ability to count cards gives them an edge over the casino’s advantage in games like blackjack. "We know who they are," he said.

Card counters are able to turn the 1-2 percent advantage of the casinos into a 1-2 advantage for themselves.