I get around 20+ messages on LinkedIn every day.
Most of it is spam.
Private messages often become the dark underbelly of a community. It’s a place where members get spammed, receive unwanted sexual advances, and personal attacks.
By nature, you won’t know what’s happening in private messages unless:
a) You track the volume of messages members are sending to other members. You can zero in on any high-volume messenger.
b) Members report abuse of private messages. This requires a clear policy and (ideally) a one-click button from members to report abuse.
Most people don’t need another inbox. If you can turn off private messages you probably should (or at least restrict it as a privilege to more senior members).
If you can’t, you need to frequently be clear about the rules of private messages and encourage members to report violations of those rules.