Most bulletin board systems track and display the post count -- its fairly standard. It true that not every post may be of high quality, but in general, those members with higher post counts have at least shown some level of dedication and loyalty to the FT community. I think most members of a bulletin board community would appreciate this.

Tracking only the join date or membership date is not sufficient as there are undoubtedly many members who have joined, but only lurked since joining.