The blogosphere has been doubling in size every six months or so - and is now more than 100 times bigger than just three years ago.

Technorati's David Sifry writes that the company is now tracking over 50 million blogs (via Micro Persuasion), and the number is doubling every 200 days. From January 2004 until July 2006, the number of blogs that Technorati tracks has continued to double every 5-7 months. Moreover, some 175,000 new blogs are being created each day; that's more than 2 blogs every second.

Blog posting volume continues to increase, with some 1.6 million posts per day, or about 18.6 posts per second. That's double the rate of a year ago. The most common times for English language postings is 1-5 p.m. (Eastern time), with another spike at 8 p.m.

Some 8 percent of new blogs are spam blogs (splogs) that get past Technorati's filters, until they're discovered and are removed; and seven of ten pings that Technorati receives are from known spam sources.