1. Because there are at leasst 10 ways that nonprofits can use blogs (see this great post from Britt Bravo titled 10 ways nonprofits can use blogs)

2. To form and strengthen relationships with constituents through conversation.

3. To establish themselves as thought leaders in their field.

4. To establish themselves as dynamic sources of valuable information.

5. To connect with other players in the blogosphere.

6. As a source of authentic, dynamic, responsive voice for communicating with stakeholders.

7. To increase their discoverability, search engine optimization, etc.

8. To increase their own knowledge of the field they are in and their ability to communicate about it.

9. To make their communication more portable and reusable than emails that get lost, etc.

10. Because everybody is doing it! (just kidding!) Because the more people that participate in conversation the more that we can shift public discourse towards being inclusive, representative and effective. Easy self publishing and technological facilitation of easy discourse is democratizing.