The so called Long Tail is an important concept in understanding the keyword phrases that can bring in traffic to a website. The Long Tail is probably more important to forum’s traffic than a regular website.
Here is a video clip from Rand Fishkin from SEOMoz that explains this concept and its importance:
In this blog post, Google point out that “20% of Google search queries are ones we haven’t seen in the past 90 days“. This just shows how important the long tail is!
Forums are very well placed to take advantage of the long tail searches due to the tremendous amount of user generated content. To take advantage of it, it is important that all of the forums content is indexed by the search engines.