Actually, almost any bank would hassle you about withdrawing 750,000 dollars unless they know who you are. Most people who deal with these sums of money have already proven to their bank that they are not scamming anyone, so this situation is somewhat unique. Once the developer sends them proof, he will never have to again.
Deposit fraud is a huge problem, and costs banks millions of dollars a year. It can also be used to launder money, which is often attached with more serious organized crime. In the case of Paypal, it can be used to steal money (which has happened to me before)
All banks do what Paypal is doing here. They usually just do it when you are opening an account.