From Scripting News:
Consider the sequence of developments in publishing. In the 70s, to run a publication you needed a million-dollar printing plant, or you needed to lease time on one, to print and distribute your publication. In the 80s, with the advent of laser printers, GUIs and desktop publishing software, the cost dropped to $100,000. So more people could publish. In the 90s, publishing technology took off in a new way, all-electronic, and the cost dropped to a few thousand dollars.
Enter weblogs, and the cost drops virtually to hundreds of dollars, maybe even tens. If you want to do a publication, all you need is the time to write, and an idea to write about. The number of publications goes up every time the rules are rewritten.