This gets to one of those changing cultural issues, namely, privacy. Within the memory of middle-aged adults, a person's reading habits were considered to be private information, shared with only a few close friends. After all, what one reads discloses who one is. (Although it's not necessarily a perfect match. For instance, some people regularly read books with which they heartily disagree -- precisely because they want to learn about (or laugh at) a different point of view.)
But upon consideration, this kind of self-disclosure comes more naturally than other kinds. After all, I'm a book-pusher both by inclination and by profession.
Library Thing is but one of several book-sharing applications out there. The main reason I haven't signed up for it before is that I already have enough trouble keeping my Facebook Visual Bookshelf and the "Books" part of "Interests" on MySpace up to date. So I decided to make this list something different. Instead of adding books as I read them, I'm listing some favorites. These books aren't necessarily ones I've read recently, nor are they necessarily books I own. For example, one is from the bookshelf of my second grade classroom.
In general, I greatly prefer Library Thing for its flexibility, ease of use, and robustness. I like the ability to edit all parts of the record, especially the ability to easily change the cover to match the book you're actually thinking of, and even upload a cover if need be. The one thing I don't like is the free version's paltry 200-book limit.
Just for fun, while we're on the topic of book lists, here are a couple of websites that list books owned by couple of more famous people:
Thomas Jefferson (1783)
Rudolph Valentino (1926)