Blogosphere stalled?

Valleywag reports this morning that by putting together Dave Sifry's State of the Blogosphere reports with some comments to Business Week, they reckon the blogosphere has stalled at 15 million active blogs. Why?

Well, we already know that more people abandon a blog than continue it. According to Forrester (sub req'd), in the UK in June 2006 5% of people online have created a blog and maintained it; 6% had created a blog and abandoned it. To imagine the blogosphere continuing to grow indefinitely we would have to believe either a change in that abandonment/maintenance ratio or a limitless input of fresh bloggers at the top of the pipe. The former is plausible; the latter clearly not, and the stalling of the blogosphere in this context becomes an almost inevitable question of "when?" rather than "why?".

Perhaps the question then becomes why more people abandon their blogs than keep them. At that point, we are into the realm of speculation and anecdote. I have seen blogs abandoned on grounds that the writer has said everything they came to the medium to say. I've seen them abandoned as the first flush of optimism that the writer was sitting on the next Buzzmachine evaporated. I've seen them abandoned for personal reasons (kids, marriage) as well as professional (new, less blog-friendly, job). And most often I've seen them abandoned without any explanation.

Why, after all, do we do it? If we really had a good answer to that we'd be in a better position to understand why so many of us stop.