It happens all the time, on all cam sites
It boils down to (usually) the fact that everyone who appears on camera has to have a signed model release on file with whatever cam site. So the noob model whos been fucking her bf on chaturbate comes to mfc (where there are no b/g cams) and fucks him here not realizing it's not allowed and that there's no release on file for him. Models that have a girlfriend on with them cause she curious about possibly being a model etc. Thats the most common form of violation, no release on file.
In the case of studios it works like this:
You open a studio account & the host cam site grants you a degree of trust. Relying on the idea that you won't do dumb stuff because it puts both at risk. If a studio has 10 models & it gets a fine it could be based on something like 2k per model even though only 1 model was the offender. And if they really fuck up their acct gets locked, all the monies paid to the studio acct to then be dispersed to the models is frozen, so not only is the cam site pissed at you but all your models who can't get paid now. Another reason to remember that payoneer and other services like it are not banks & not bound by ordinary fiduciary rules so don't treat it like a bank, get paid & take all your money out, we all remember epassporte right ?
I have seen studios abuse this trust in the past, 1 model leaves & another comes along, maybe she doesn't have the right papers or whatever but the studio lets her cam under the previous models name. Some aren't even smart enough to swap the old pics on the profile for new. Stupidity catches all.