There's a great post today from Michael Gilbert: Online Social Networks Are Not Mailing Lists.

I love it because a) it's true and b) he ties it to the larger issue, RESPECT. He argues that thinking about how to use social networks as communications channels is disrespectful. It undermines the community your stakeholders want. This line sums it up:

The genuine respect that is the key to success takes this form: First use your resources to build community and only secondarily use community to build your resources.