According to Valleywag and Technorati the number of active blogs have stalled at 15 million,

I guess that's the end of the inexorable and exponential expansion of participant created content?

I don't think so...

Blogs only represent a small fraction of what can be considered content creation and participation by...well... participants.

Other forms of content creation include comments, video, audio and lifestreams. Participation, however, includes an even broader set of 'gestures' such as clicking, voting and rating.

Web 2.0 and Media 2.0 are alive and well.