The number of participants in a particular open source forum, is just a fraction of the total number of developers actively using that product. Think of how many open source projects you use yourself, and compare that to the number of forums you actively participate in. Helping to ignite an open source community may be as simple as asking a few questions.
Looks like I'm on the short list of Ignite speakers vying for 5 minutes of fame in the keynote this week. Am doing a quick piece on how you can contribute to the open source communities you are involved in and really make a difference.