Blogging Until the End of the World

There is a film by Wim Wenders, Until the End of the World. In it, a scientist works on a way to let people record their dreams onto video. The characters become enamoured of watching their own dreams. Some become more adicted than others. The dream watching enacts a kind of strange narcissism.

Are blogs a similar kind of narcissism, combined with public display?

I've been asking folks about why they blog and what they blog. The answers so far have been mainly in two camps:
1) to let friends and family know what the person is up to.
2) to have a place to write something down to keep ideas from slipping away.

But these reflections are available to the WHOLE web. ANYONE can look at them. What makes that seem safe?

Are blogs effectively a broadcast medium, then? They include the facility to comment, but it seems few people do. The small number of folks i've communicated with about blogs have said that while they track other blogs, they don't usually leave comments. They'll email the blogger. So the use of the blog as a forum for public exchange isn't there it seems.

Or does it depend on the kind of / context of blog?