This is a personal journal broadcast on the internet. The term originally used was Web Log (or Weblog), like a ship’s log kept by the captain. By extension, a log became a personal journal, and a Weblog a personal journal broadcast on the internet. In 1999, a web designer, Peter Merholz, was the first to shift from Weblog to “We blog” and thence to “Blog”, which was shorter and above all less politically correct if not subversive (onomatopoeically, it suggested the vomiting of information). The word was quickly adopted and institutionalised by Blogger (one of the first blogging platforms) (1). Over 162 million blogs had been counted worldwide by May 2011 according to BlogPulse, and the number of people reading them is increasing. One French source put that increase at 28% per year in January 2011, with 12 million people in France alone connecting to a blog every day and three quarters of them every month. Reliable statistics for other countries are hard to find, however.
(1): For more on the origins of the blog, see the excellent work by Scott Rosenberg, Say Everything.