Most people with a MySpace page or Facebook account have, at some point, looked at their friend list and wondered what they really know about any of these people.
Now, there's a new way to find out more.
Social cataloguing, or "social networking with a topic," has exploded online, allowing users to list their possessions and chat with people who own the same stuff.
The offspring of social networking sites, these sites for collectors attempt to bring together existing communities of like-minded individuals.
"The way we connect with each other is much more complicated than friend (or) not friend," says Tim Spalding, founder of LibraryThing, a site for book collectors.
"One of the ways - with book people particularly - is through shared taste."
On LibraryThing, users catalogue their personal book collections and are introduced to other members who own the same tomes. Such sites now exist for people who like everything from wine to porcelain figurines, providing a clubhouse for connoisseurs and a wealth of information for marketing execs desperate to know how people spend their money.
At Corkd.com, members list the pinots and chardonnays that line their cellars, while beer lovers chronicle their bottle collections on Coastr.com. The social cataloguing site 43Places lets seasoned or wannabe travellers keep track of where they have been and where they plan to go next, sharing travel tips with those who share the jet-set life.
Squirl.info is for collectors with more bizarre tastes, from ambient music to vintage GI-Joe, while Allconsuming.net lets people keep track of anything they enjoy, from food to shoes to specific people.
Mr. Spalding originally started LibraryThing so he could manage his own books, particularly his collection of Greek and Latin literature.
"I wasn't initially thinking that the social aspect would be that interesting, but I was very wrong," he says. "If you and I share 40 books, I could engage you directly, or I could just check out your catalogue."
Twenty-eight-year old Holly Hill, whose collection currently boasts 2,246 books, also started using LibraryThing to get organized, but now visits the site to chat or get recommendations. "Reading is such a solitary hobby that it's neat to connect with people," says the Prince George, B.C., software developer.
At home, her bookshelves are overflowing, but her online collection is neatly organized alphabetically by title, revealing her ownership of The Penis Book and apparent penchant for Black Stallion novels.
Her tastes may not stand out among other registered users, but retailers and marketers are salivating over the amount of consumer information people like Ms. Hill are posting on such cataloguing sites.
"The thing that most interests us about LibraryThing is the data it produces, what it tells about readers," said Richard Davies, a spokesperson for Vancouver's Abe Books, which recently bought a 40 per cent share of the site.
Abe Books does not directly market to LibraryThing members, but uses aggregate data from the site to produce a Book Hints service for its own online customers.
Mr. Spalding recognizes that social cataloguing has "obvious commercial value" but says that protecting sites' independence is key to maintaining trust among users. He sells only anonymous data about his users' taste, and does not even collect demographic information from those who sign up.
Instead, LibraryThing makes money from membership fees and by selling bar-code scanners to users and cataloguing tips to real-world libraries.
But even without a corporate presence, not every social cataloguer has pure motivations.
One author started a bunch of fake LibraryThing accounts where she gave her books positive reviews, and Mr. Spalding says others are simply there to show off.
"There's exhibitionism, there's bragging, there are cries for help," he said. "People will list books that I would not admit to owning: self help or strange pornography. I guess they want to find other people who are like that."
And, as with the more traditional social networking sites, some social cataloguers are trying to accumulate a list of sexual conquests.
Mr. Spalding's brother has used LibraryThing to meet women, employing a kind of "what's a nice reader like you doing on a site like this" approach.
"If Oakes Spalding propositions you, know who it is," jokes Mr. Spalding. "He, like me, does relate to women about books."