User-generated content is all the rage! Unfortunately, there is no such thing.
Users are not interested in generating content.
They are interested in communicating.
Blogs are not content. They are communication.
The 15 million bloggers out there do not consider themselves publishers. Probably only a few hundred or a thousand of those bloggers are publishing. The rest of them are communicating. Just like they communicate over email or telephone or IM. They are regular folks who are just talking.
When the communication is captured so it is not ephemeral, you get what people are calling user-generated content. But it is not content at all, it is communication that has been recorded for all to see.
This distinction is subtle but very important. Dont expect your users to generate content. Instead, support their efforts to communicate.