Library Thing was an application I was aware of, but I really didn't see a lot of point in cataloguing my own books. To me the main point of a catalogue has always been to find the book you want, and although my family has an extensive collection, we can usually find the ones we want (and even if we can't put our hand on them immediately it is always a good excuse to browse the shelves).I admit that until I had a play with it, I was unaware of the other features it contained, such as clicking on other's review of the books, or that one could download records from such a variety of sources. I can see the attraction of having recommendations and seeing other similar books that are around whether in, or out of print.
With great trepidation I uploaded details of a few of my books - including the book my father wrote on the Overseas Rugby Club - well it has to be the star of my collection :) Once my records were loaded it was interesting to see how many other members had read the various books - and their comments. Obviously it was no surprise that mine was the sole entry for my Dad's book ... however I was surprised that the most read of the small selection I had chosen to input was "The Medieval Tailor's Assistant", a book on making clothes for re-enactment.
Which brings me to one of the perceived benefits of inputting Library Thing data into your OPAC mentioned by John Wensler in his article Library Thing and the Library Catalog - that with Library Thing's large membership more tags will be available for each book than will be available if only your patrons input tags ...it depends on the book. For a specialist book, or a specialist library your own patrons may put in more relevant tags to help their co-user find the book.
I was also wary of the comment that the recommendations for what you would like to read would be more accurate than the famous online bookseller, not being based just on what you had bought (Social Networking for Bookworms). However unless you input all your books onto Library Thing I suspect that this will be similarly biased... I am sure I am not the only one that carefully selected the books that I wanted to show to the world as books on my bookshelves - no cheap and 'cheery' whodunnits here :)
In conclusion - an interesting tool to play with - possibly useful in a library situation, but definitely as an 'added extra', not in place of traditional records.