Matt Gemmell has an excellent post on the community that has built up around App.Net and why he'd like you to consider joining.

The practical effect, which I notice daily, seems to be that people are more willing to participate in conversations, and also more careful about how they express themselves. Such a broad generalisation has no hope of being true for everyone, but it’s been my consistent perception during the months I’ve been using the service.

— App.Net for conversations by Matt Gemmell