It looks like the amount of total SL Forums/SL Answers posts are slowly declining, according to the daily Forum Post Counts site which tracks post counts for each SL site. Perhaps we may see good growth later in the year with all the new features Linden Lab have been/yet to come features into the official Second Life Forums.
SLUniverse Forums posts are increasing each month and more members are joining every month there. Other well SL community forums seem to be going at a good steady pace. Many SL residents enjoy reading and writing feedback on lots of interesting topics.
Check out post counts by month for 2011 so far and the latest graph shows a big drop in numbers since early 2011.
March: 19, 983 posts
April: 14, 514 posts
May : 13, 633 posts
June : 10, 292 posts
Threads: 57, 615, Posts: 1, 302, 129, Members: 17, 827
Total posts 65, 973 | Total topics 6, 965 | Total members 3, 016
Discussions: 2, 021Messages: 98, 017Members: 260
Threads: 13, 873, Posts: 378, 119, Members: 2, 322, Active Members: 175
Daniel Voyager 
