I think the fact that checks worked (and continue to work) for decades says a lot about how, generally, most people are pretty honest. Sure there's some fraud,

I think the fact that checks worked (and continue to work) for decades says a lot about how, generally, most people are pretty honest. Sure there's some fraud, but it wasn't on a level that made the whole system untenable, like almost happened to PayPal. It's not like credit cards or other forms of transferring money are immune to fraud either.