At no disrespect to Evan Williams, I think the nail went into the coffin for Odeo when its own creators weren't its best users, i.e. they didn't podcast themselves, so their podcasting tools failed to deliver for the rest of the podcasting community.
Coming out of college, I had a few friends ask if I wanted to join their startup. I ended up politely declining on the grounds that I simply wouldn't have been a "good user" of what their team was trying to build. I essentially told them, "How can I understand and champion our users if I'm not a user myself?"
This same philosophy applied when I had to turn down Microsoft one summer because I felt I wouldn't be happy and, therefore, couldn't give my best working on a product that I didn't use.