So reduce the question to this: does the impression you get from a blog harmonise with the picture you would build up from face to face interaction with the blogger? Making it sharper: if you like a bog would you like the person? If you hate a blog would you hate the person?
One thing I like about blog-interaction is that allows people to skirt around issues that complicate face to face friendships. I'm thinking of age and gender. Disability is another one. Perhaps physical attractiveness is the most significant. I don't mean people want to be prejudiced against people much older or younger, or a lot more or less pretty, or self confident than themselves. But in real life it does add a layer of awkwardness: especially early in a relationship.
One final point; what are the characteristics that make a blog-personality attractive? In the discussion I linked to above someone says:
People may selectively report details of their personal lives, but they give themselves away in other ways. For me, the two most revealing are conflict management and humor. People who seem respectful, secure, and funny online tend to embody those virtues in real life.
This seems good.
I have a feeling (or is it a hope) that some people come across a lot worse online than they would in real life. They rant in a mad-eyed way online, when in real life they are probably a lot more easy going. You know the kind of person I mean (not any of you lot).