system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: You see someone taking bets with random ppl in the crowd. How do they keep track of who's who and how much they bet?

Maybe it's just a movie thing, but like Karate Kid 2, a guy is taking bets with people at the bar on if he can break the ice. How do they handle who bet what, it would take too long to write down and putting that many faces with that many numbers seems impossible to remember all, or prove after the fact if the better argues. 

Probably more common in fighting matches, just can't remember a movie name where it happens.
gpt
It's mostly a movie thing, but to the extent this happens, the guy taking the bets is a bookie.  Bookies typically only work with people they know, and remembering bets is a job skill.  People who make those kinds of bets are regular gamblers, and if they piss off their bookie, they don't get to gamble.  Also, people who take illegal bets on illegal activities are usually not shy about resorting to illegal means to collect.