Blogging is really a form of self-publishing and has become far more popular than ever envisaged, although it is regarded by many as being in decline these days.
Blog writing has become less popular in the last year or so as people have swapped over to social networking e.g. Facebook, Twitter etc. Maintaining a blog seems a little more old fashioned - after all the first blogs appeared in the 1990s. (Explore some interesting social networking stats here)
A recent estimate of blog numbers gives the number of people using Wordpress as 64m websites read by 371m people each month. An estimate gives Blogger blogs as 76m.
Here is an interesting graphic - it basically relates to bloggers in the US and shows what people are using blogs for. Original page is here.