I think that, used effectively, weblogs could become important in online community building and support. By offering weblogs to members, like you find at eCademy, you offer someone the ability to have a "pedestal" where they can share their thoughts without dominating discussion forums.
For support, I think a community-specific Weblog could be a one-stop shop for community related news, updates, support, perspectives, related news etc. If the community leaders use the Weblog consistently, it could be a great culture building tool, allowing new members to quickly get a feel for the "feel" of the community through the Weblog.
With this Weblog plug-in, a site could allow a member to start their own Weblog with the press of a button. Each one has categories support, comments, email subscriptions, RSS feeds, spell checking, links, etc. Pretty impressive.