In my experience running forums ranging from
dinky to
huge, I've seen what you're talking about.
Typically, though, that issue is one to be dealt with when there is a reputation system in place (we've nixed that option here) or where the forum is set up specifically as a question and answer forum (like askmehelpdesk.com, allexperts.com, etc.).
For now we'll leave the post count in - but watch things closely.
The other issue that I am confident is key in having a top notch forum without
trolls is good moderation.
We will stay ahead of the game by making sure that we have good moderation coverage as the site grows.