I'm a software developer, and I want to make a website that allows users to sell bitcoin instantly for paypal cash without the hassle of an exchange - I don't even want to make a profit from it. The idea of it is to be a 100% fair exchange, instant, and no account/signup needed to encourage more people to use bitcoin.
Regardless, I was thinking last night and wondered if money laundering here is a concern? For example, a user stole bitcoins and sold it with my exchange. Is it the sellers responsibility to ensure funds are clean (since we are dealing with fiat cash)? What if someone buys bitcoin with dirty money and tries to sell the bitcoin on my exchange for clean the money? Would the seller be in trouble even though there is know way to know funds are legit? I am in the US.