I'm guessing that if someone has been exchanging PM's about sources, he hasn't read the site stickies or taken them to heart, and he is setting himself up for a world of disappointment.
You would have no way of knowing it, but the specific person you are describing has two completely different personalities. If you're a newbie, he comes off as this really well-connected veteran with lots of sources. But if you're a vet yourself, he presents himself as an innocent who is OH SO GRATEFUL for any little tidbits you can share with him -- like sources, whose identities he will then steal.
When I say "you" this is to everyone -- we don't read PMs routinely, but you can still get caught if you abuse them. When we get complaints, an Admin can change the scammer's password, log in to his account and dump his PMs.
Can't be done by a mod -- it has to be an Admin. But you should understand now that when AAP told you "no sources in PMs," he was not bluffing.