SEO and community sites

[amandahx2]

I'm looking for feedback from anyone who has launched a community site to see:

1- what kind of SEO benefits you've received and how were you able to measure it and correlate traffic to the community site.

2- what community site platform did you use (i.e. Drupal, Lithium, etc.)

3- does the platform you use affect SEO one way or another (is one better for SEO than another)?

[Catalyste]

I did use Buddypress for Wordpress once for a Thematic community website. This was a small personal project but I was great since it doesn't took to much time to build and was compatible with Wordpress SEO plugins.