LinkedIn recently reported as part of its initial public offering package that most of its members don't use the site on a regular basis.
The fact was picked up by Jim Edwards in a recent article on bNET, recently. It's an interesting issue on at least two levels:
1) First, because LinkedIn is revealing they can't differentiate between active, inactive, and even dead members
2) Secondly, because (I would posit) it does not impact the user experience of an active member - at all.
If you actively participate in group discussions on LinkedIn, does it matter if there are only 10-20 active participants?
Would you rather have 40-50? Or 200-300? I don't think it impacts the user experienc within a discussion group. I currently belong to both national and regional discussions. This story was reported on in a regional discussion group of which there are less than 700 members. There are probably "lower limits" below which a discussion group seems to become a bit lame, but I'd be hard pressed to say what those limits are.
I think quantity and quality are two wholly different aspects of any online discussion, and I for one am perfectly happy having 40 intelligent users in the conversation provided the conversation "works for me."