First a few random notes on some of these sites:
Easily the biggest of them all. It claims 228,000 members and 15 million books. What struck me when sifting though the blog posts was the number of people trashing the design and usability of the site, usually by people recommending Shelfari. I keep looking back and forth at both sites and still an unclear what they mean. They both have a similar appearance to my eyes.
LT is one of the few that charges for its service: it's free if you have only 200 books; a life membership can be had for $25. 40% is owned by AbeBooks. Random House is a partner for an early book review program.
A relatively new site that has attracted a lot of attention. It's unclear to me how many members or books it has. I'm assuming those numbers aren't prominently placed because as a new site they are still building up their membership.
I imported my library from LibraryThing with some problems. I have a number of books in foreign languages (Chinese, Japanese, Vietnamese) that I manually loaded into LT because they couldn't be found in places like Amazon and I had to look them up in online library catalogs in China and Japan. The titles include Chinese characters and Japanese kanji. Shelfari couldn't load any of these.
Shelfari doesn't allow for manually adding books, and to me, that is a serious weakness. I'm sure it's a problem for serious collectors who have unusual items that can't be found in the standard online catalogs.
This site has been lauded for its many features. It claims over 1 million books. Based in Hong Kong, it's not surprising to see a lot of Chinese members here. Would aNobii easily import my LT library with Chinese language books? I can't answer that yet. I tried to import my library several hours ago and it sent back a message: "Got your order! You will receive an email from us once your data is ready." Every other site took only a few minutes to import.
I see only 32 groups, far fewer than the other large sites. Like Shelfari, aNobii doesn't allow for manually entering a book. You have to either import or find it, otherwise you're out of luck. Not good news for bibliophiles! I can't take aNobii or Shelfari seriously until they include this option.
I'm not a fan of the graphic of books across the top of the page. It looks unkempt and unsightly, but like the debate over the design of Shelfari and LibraryThing, I suspect beauty is in the eye of the beholder. GR imported my LT xls file, but not the cvs--and of course it couldn't handle the foreign-language books. Thankfully, GR allows for manually adding books.
BookTribes claims 1,500 members and 2.5 million books. That's 1,666 books per member. I think there is a credibility problem here, unless there is some bizarre explanation of why so many books could possibly be in the database with so few members. Are there importing or exporting options I'm not seeing? Or manually entering a book? I can't see the attraction of this site.
Some numbers (Blogsearch numbers are the total claimed number; not the actual number of viewable entries):
Social Library Catalog Blog Numbers
aNobii has been coming on strong the previous month (June 2007), with triple the numbers of Shelfari and double the numbers of Goodreads. But LibraryThing is still far ahead of all the others.
I know there are a lot more sites, but I'm not including them yet. Stay tuned.