In the historic world of high-stakes rubber bridge, you're right - players would cut for partners after each 'rubber' game so your partner in crime might soon b

In the historic world of high-stakes rubber bridge, you're right - players would cut for partners after each 'rubber' game so your partner in crime might soon be your opponent. I'm sure there were occasional big-money scams like all situations involving gamblers and money generally. Roald Dahl wrote an amusing short story about one possibility. In the modern world of competitive duplicate bridge, there are occasional collusion-based cheating scandals - the most recent one I'm aware of involved a communication system via position of the pencils with which the pair involved kept track of their score. By far the most famous scandal was a pair of English players back in the sixties communicating the number of hearts in their hand (enough to give a winning edge) with hand signals. Nowadays good records are kept and cheating tends to come to light eventually. The apparatus used in top tournaments is different from a casual game and meant to prevent collusion, and also, with the diagonal screen, make it harder to tell whether any hesitation came from your partner (reducing deliberate or unintentional inferences). In big tournaments with lots of players, because hands are duplicated to be played lots of times, it's not uncommon for players to be on a 'wire' i.e. deliberately or by overhearing learn some features of a hand they haven't played yet. It causes a lot of outrage and controversy but it doesn't ultimately matter that much. The most important matches are between two teams and things are arranged to reduce the opportunity for the pairs in a team to communicate with one another. Since I'm writing a pretty long post here, I'll also mention that computers still don't play bridge especially well, so the problem of players getting computer assistance, such a concern in chess, doesn't feature. All in all, preventing cheating in bridge is kind of an ongoing but not particularly high-profile activity. There's an obvious solution to make cheating even harder - keep players physically separate and make them do everything from a monitored computer terminal, which could also do things like introduce delays to make everything happen in tempo. But the administrators obviously think that would be pretty unpopular and prefer to keep it a card game.