Google has suffered a rare setback, pulling its ads on Orkut after a barrage of complaints called into question the search giant's ability to capture a foothold in the red-hot social networking arena.

Google decided to pull ads from Orkut after SaferNet, a Brazilian nonprofit complained Orkut pages featured ads for child pornography, according to a Wall Street Journal story. Google said it removes illegal images when it becomes aware of them.

Although Orkut remains somewhat unknown in the U.S., the site attracted about 25 million people in August, according to comScore. Google, which said only about one percent of Orkut pages had ads, said it was using its presence in Brazil to test ways to monetize its social network. Those tests are now on hold.

Alexandre Hohagen, a Google executive in Brazil, said the company was working closely with authorities to stamp out child pornography on Orkut. Hohagen did not say when the ads would return.

The setback comes at a bad time for Google, with its rivals working feverishly to gain traction in the social networking space. Yahoo! is working hard to perfect Mash, its second social network designed to threaten MySpace, while Facebook continues to rumored as an acquisition target, despite the fact that Microsoft CEO Steve Ballmer chided the company as part of a "fad."