I have been blogging now for almost 3 years (My exact first post was Jan. 8 2003 in my old blog). I have blogged on and off but for the most part have been pretty consistent, trying to get out 3 or 4 post a week.
I wonder how long the average blog runs. I wonder how many blogs are already abandoned. If you try and get some of the more popular names on blogspot you will find many blogs that are simply abandoned. I wonder why blogspot doesn't just go and reclaim dead blogs. Maybe for posterity? Couldn't they just archive the pages somewhere else to free up the urls? I would think they could send an email to the blog owner telling them they need to confirm they still want the blog, and then delete it when there is no response. This could happen after a period of inactivity, say 6 or 12 months.
I found some statistics here and here but nothing I would say as definitive. My bet is that the average blog only last a few weeks before someone gets bored and decides they no longer want to do it. I bet that the percentage of dead blogs must be very high, my guess would be about 85% of blogs that were once started are now dead. Anybody else have some guesses.