It may a lack of being able to think dynamically. The set of blogs in operation will change rapidly - I expect that after the blogosphere matures (which I do agree with Russ Smith that that will be fairly soon, within a year) there will be a lot of turnover. But there are way too many people who do this because they must rather than because they need money for there to be only a "few survivors". Blogs have been around long enough to see a number of good writers give up, but over time accumulating so much pent up verbiage that they are compelled to start writing again. I suspect I will be the same way. I try to write every day, but sometimes it's a burden. Other times I can't type fast enough to express what I have to say. But ultimately this blog is about satisfying me. Part of that is providing something pleasing to others, but that's not the only thing. And I suspect that most bloggers are the same way. People can walk away or ignore you in person, but if you've got a blog they can't shut you up.