With blogs, the feeling you get is typically the voyeuristic thrill of rooting through a closet full of diaries.
I'll admit that I'm a filthy, filthy investigator. Human nature is a curious thing, and my curiosity is always dragging me off in these kinds of directions. Careful guessing can produce surprising results with Google, including lots of information that people will often not realize is available to the world.
Case in point: I emailed an instructor of mine fairly recently at a few email addresses I managed to glean from Google (or guess from information gleaned thereof). He was surprised, part because I used an email address that had never been given out, and part because the domain it belongs to was not one that had gone "public" yet. Google's a strange beast, but one I'm glad to have around.