Library Thing

I have had a bit of a play with Library Thing.
I'm not that concerned with cataloguing what books I own (that info is sort of in my head), but I was interested to see the social side of it and how I could use other people's reviews and tags to search for books I might be interested in.
I think I found it most useful to look at other people who had reviewed or added the book I had added and then look at their libraries.
There are so many people though with such huge libraries I'm not sure how relevant this will always be. The forums and groups might be a better way to go for this, but I've never really been that social online. I prefer just to look quietly and not interact...
A friend of mine got really excited about Library Thing a few years back as she has a huge collection of science fiction, romance and fantasy. But she was only to be disappointed by the fact once she got to a certain size library it required her to pay money to continue - a bit like Flickr.
Not a drama if that is really clear up-front, but annoying if you have invested time and effort into it thinking you can continue to use the service.