This last Monday, Facebook began gradually introducing a new feature, Marketplace, which, similar to Craigslist, lets users buy and sell items. The app will be first introduced to users in the U.S., Australia, New Zealand and United Kingdom, and will also be available on the desktop in the next few months. Because most Facebook users access the site via mobile phones, Marketplace will provide better location data for matching buyers and sellers than Craigslist. Since the launch, however, Facebook has been dealing with illegal items for sale.

Bloomberg notes that, in 2007, Facebook launched a similar service, also called Marketplace, but sold it in 2009. According to The New York Times, the latest version of Marketplace had a problem within hours of going live: users posted ads for guns, sex acts, drugs, dogs, and baby hedgehogs — all illegal.

Facebook director of product management Mary Ku apologized for the mishap, “saying that a technical issue had prevented Facebook’s reviewing system from identifying posts that violated its commerce policies and community standards,” and promised that the company would fix the problem.

It echoes a similar problem reported in July by Web designer Mike Monteiro, who “started a campaign to help monitor the social network for sales of guns,” reporting “about 500 posts or groups that violated Facebook’s ban on weapons sales in the past month.” He said “the website had taken down only about two-thirds of them.”

Ku notes, however, that more than 450 million people are already visiting buy-and-sell groups on Facebook. EBay shares also fell “as much as 3.5 percent to $31.75” after the Facebook announcement of Marketplace. NYT points out that, “Facebook has natural advantages as a digital bazaar,” whose “core purpose as a social network would allow users to more easily avoid anonymous strangers and dubious deals that are available on sites like Craigslist, which allows for anonymous posting.”

Not everyone is enthused, however. Former Yahoo executive Dan Rosensweig, on a CNBC appearance summed up his skepticism: “Why would I leave Amazon’s marketplace or eBay’s marketplace or anybody else’s marketplace to go to Facebook unless I thought I could sell more or make more money?”