Amid charges from LibraryThing of planting blog comments, social networking site Shelfari now belongs 100 percent to Amazon.com. Yet so, too, does AbeBooks, a partial owner of LibraryThing.

Amazon.com today acquired Shelfari, a social networking site for book lovers, less than a month after buying AbeBooks, an online retailer of used and rare books. AbeBooks holds an equity stake in LibraryThing, Shelfari's chief rival.

In February 2007, Amazon obtained partial ownership of Shelfari, a site that has garnered excellent reviews from some online bibliophiles, who have praised the ease of use of the Web site's interface.

Yet LibraryThing founder Tim Spaulding has been accusing Shelfari of "astroturfing," or planting positive comments on blogs. Spaulding claims to have evidence that Shelfari staff members are writing some of the comments under assumed Web handles.

In one blog posting about Shelfari, for example, Spaulding contended that "it's icky [to] go on and one about how much you 'love' Shelfari without mentioning you've been paid by them."

"Shelfari is a bad actor. Considering that they're the only well-funded site, with a reported $1 million from Amazon, their spamming and astroturfing is particularly despicable," Spauling wrote.

In his company's defense, however, Shelfari CEO Josh Hug responded that any astroturfing on Shelfari's part was the work on a Shelfari intern -- and that it's no longer happening, anyway. "As for the astroturfing, that was an unintended work of an unexperienced but well-meaning intern who failed to make himself known as he commented on blogs. That was not our intent and we were unaware that was going on. It has stopped," Hug remarked, in a comment also posted on Spaulding's blog.

With today's total buyout of Shelfari, though, Amazon seems to be placed in an even more awkward position.

Although LibraryThing still leads Shelfari in the book lovers' social networking space, with over 200,000 unique visitors per month, according to figures compiled by Compete.com, Shelfari has been closing the gap, enjoying a surge of additional visitors since April while LibraryThing's numbers have slid.