The huge problem with open source software is that there are no sales numbers to show how many people are using it. We know that WordPress.com hosts over three million blogs. We know EduBlogs powers nearly 200,000. But how many sites are hosted using the original, downloadable, self-installed and managed version of WordPress?
Now, the automatic update notification system in WordPress gives answers to that question and others. Most hugely: over 2.6 million sites are hosted on WordPress.