In VB when you report it, it copies the body of the PM into the email report, thus the moderator can see the PM. The user has given explicit permission for them to view it by clicking the 'report button'. So there shouldn't be any privacy issues, then the moderator can decide what to do.
In this case, a clearly blatant spammer sent me a PM. I imagine they PM'ed other members too. This is mass spamming and if the users don't have an easy way to report it it will just continue.
Just my 2c.