Gambling and magic tricks have a role in interaction design but I have trouble working them in to the syllabus without encouraging illegal behavior on campus.
The MIT Blackjack Team has a good FAQ on counting cards. tl;dr: Yes, it’s legal to count cards but not with the aid of any external device or help. In Las Vegas the casinos are privately owned and they are allowed to eject anyone they suspect of counting cards.
The scheme my friend used to get us free food and drinks in Tahoe casinos was to be seen as people gambling (and losing) a lot of money; we’d get vouchers for free food and drink at the house restaurant. The (legal!) scheme was betting “Don’t Pass” at the craps table more often than not. That is, we were betting that the person shooting dice will lose and the house will win. This is how casinos make money — the people gambling lose more often than the house, so the house wins more money and makes a profit. When the house notices you’re winning more often than losing (and cutting in to their profit) they change the payoff for winning a “don’t pass” bet or simply close the table. However, we still had our vouchers for free meals and drinks!
If that doesn’t make any sense, the wikipedia page might help.