I guess I’m one to believe that what’s most important about a blog is the information provided. And if that’s true, then it only makes sense to publish that information in a format/style that is most easily absorbed and comprehended by the reader.
For example, if I’m reading a story about an oil spill off the coast of New Orleans, I really don’t care if the font face fits “thematically” into the rest of the site. My only interest is the story itself, and the quicker, the more efficiently I can get through that story, the better.
I’m more than a little troubled with the trend I see in “newspaper” blogs to use the same fonts they use in print. I can understand what the designers are attempting to do. But in my opinion, the printed-look just doesn’t translate well online. Untill such time that everyone has liquid plasma computer monitors (or some other HD interface) serif fonts will always be less readable than san-serif fonts.