This happens to me alot too. Try getting your freinds to post by sending them a note to let them know. That's what I did anyway.

the forum topics don't show up in the updates, so it's really easy to for people miss them. you will probably get more replies for picks, articles, images, etc :)

or if you make a new forum thread, try posting the first comment in it as well, to get it started. comments on forums do show up in the updates :)