I understand that many new and established members alike are reluctant to report PM spam involving secret/private source. Like you said, they don't want to be called a tattle-tell, snitch, rat, etc. But why should anyone give a fuck about protecting source spam? It's in direct contradiction to protecting members.
If you've only been a member for 3 months or less, it's a clear red flag when someone, out of the blue, sends you a PM with a source recommendation. And I'd also be highly suspicious of ANYONE, regardless of their "status", who "befriends" you in such a short period to privately promote sources. They may genuinely be trying to help you but...
Beware that sources know AAS forums provide a highly-targeted audience of people looking for AAS and eager to accept the "friendship" of those who can facilitate the process. They are going to aggressively exploit that fact for every penny that it is worth.
Again, no one is under any obligation to protect this practice. Anyone who calls you a snitch or rat for reporting it doesn't have the best interest of the community in mind. Covering up the practice only protects the secret/private sources and their ability to target/exploit newbies.