In the aforementioned case where the seller neglected to send a copy of his Drivers License, it was absolutely no problem for the FFL I was using to do the transfer. The gun was bought and paid for by me. The FFL simply said he would have to hold the gun until the seller sent or faxed a copy of his Drivers License. It was entirely my problem and my responsibility to get the required documentation. This is also part of my reason for paying for my internet gun purchases with a U.S. Postal Money Order. If my purchase should end up being stolen or if the seller refuses to comply with the law, I'll let the Postal Inspector handle the mess when it becomes mail fraud. The only responsibility the FFL has is to complete a legal transfer. I expect no more and no less.
My current FFL guy is a gem, but not quite as good as the previous one who charged me nothing. Oh, when I smoked, he would charge me a cigarette or two because his wife didn't allow him to smoke.