I too have been a blog failure over the years. I had a xanga account in college, but it made me feel narcissistic, so I stopped writing. Then I started a blog about funny things my students said, but I got too busy to keep it up.
Blogs are an important part of my family's culture though. My brother is part of a particular religious/cultural group that is very in to blogging. They often do missionary work and have access to e-mail more regularly than any other form of communication, so blogging becomes an easy way to stay connected to a larger audience. As a result, his entire community blogs and I love it. He lives in Utah (can you guess what group he's part of?) so I don't get to see him, my sister-in-law, or my niece very often, so their blogs are the simplest way to stay connected. As a result, evenings spent around the computer reading blogs is not uncommon for my mom and me.
I think they serve some specific purposes really well, but like Professor Kutz said, are more limited than the wikis. What they offer is simplicity. The dang wiki makes me want to jump out my window, but the blog is straight forward. I suppose that's always the trade off with technology though. The more capable it gets, the more complicated.
Check out my sister-in-laws blog if you'd like: hosander.blogspot.com