If you think using a CMS is only for a small business and large companies develop large and complicated systems for promoting their blogs, think again. Large and small companies both use WordPress. Even Microsoft recently moved is blogs to WordPress on the WordPress.com site. That should provide you with enough to know it is popular and wide spread.
But in case you need more information, here it is. WordPress, has recently developed WordPress 2.6 for use on the iPhone which is a large market of users. As we have talked about before with Mobile Is Coming, it will not be long before people are creating their blogs on the smartphones.
The New Year Times has their blogs running on WordPress, though they have customized the template to make it look unique for them. The Mozilla Blog, makers of the FireFox browser use WordPress as well as Network Solutions a provider of Domain Names and SSL security certificates.
There are many other companies which could be mentioned, but you get the point. WordPress is popular and continues to be used by businesses large and small.