This is what happens when I don't stay on top of the CTA Tattler. In this case the blogger here didn't play this game and immediately contacted the motorman. He's a blogger and he WILL report you!
For the most part I say nothing. Gambling is illegal anyway and other solicitation activities on CTA property. They will pick the wrong car or the wrong day and get caught. I'm definitely surprised they haven't be assaulted themselves by someone who took exception to the hustling. Especially after losing a large sum of cash.
BTW, I ran into this last week leaving 95th Street. The train just pulled from the station and he already got started. Found some people who were willing although someone was part of the shell game even if he didn't use the board. Regardless I try not to get pulled into that because I have no interest in playing.