I'm only talking about trademark law. I'm not arguing what's morally right or wrong, that's a subjective perspective. I'm not able to tell if Dreamhost and Bluehost are violating the trademark, but from what I know they are generic webhosting companies and not as easily confused with Wordpress. In my personal opinion having had a quick look at Dreamhosts page about hosting Wordpress. It seems quite obvious that they only host the Wordpress software, with prominent phrases like "optimized for WordPress" and "Recommended by WordPress.org".