A blog is a brilliant tool to spread ideas, but it’s not usually the best tool to build an online community.
A blog doesn’t allow multi-way relationships between members. It’s usually two-way, you and the member talking to each other. You via the content, the member via the comments.
A blog doesn’t show who’s friends with who. It doesn’t allow for an unwritten culture to really develop. It’s not easy for two members to have a side chat.
Worst of all, it’s all about you. If you stop blogging, the community dies. That’s no good at all.
By all means have a blog for your community, but keep it as part of something bigger. Perhaps the blog is the rallying point, like a newsletter.
A great community will inspire members to write their own brilliant blogs.