Scott Allen, in a larger post about social media in 2004, has an insightful comment about the nature of social networking sites:
The truth is simply people don't know how to use social networking sites. Pundits can say all they want to that they should be intuitive, but the issue is not the use of the site - it's the social practices online. The typical 40-something professional has around 200,000 hours of experience interacting with people face-to-face, and less than 5,000 hours interacting online. As the human race, we have tens of thousands of years of face-to-face interaction, and barely 30 online - 20, really. What do you expect? It's we who need to learn how to interact online effectively - the social networking sites can't do that for us. They're a tool - nothing more, nothing less. And most of us can even learn to use a hammer more effectively.
Any tool, whether it is "intuitive" or not has a contextual component that cannot be learned from the tool alone. I think this connection has a link to some of my comments about participation = writing in online communities. Social networking services, project management software / methodologies, personal information managers, mailing lists ... At the very least people need to spend time with the tools to understand them. But even more, we need help in understanding the context in which we are expected to work with the thing. On mailing lists, people find the voice and courage to write once they understand the norms of the community. People are much more likely to use project management concepts effectively when they understand how their organization employs the concepts to drive its business.