The recent agreement to link advertising between Google and Yahoo, the two largest search engines, is facing some tough scrutiny from regulators at the Department of Justice, according to recent Associated Press reports.

While the deal is restricted to the friendlier United States and Canada, avoiding the notoriously tough anti-trust inquisitions from the European Commission, competitors and other Internet advertisers may still pose a significant hurdle to success.

According to the AP, "Google general counsel Kent Walker said in an interview that the company was confident the Justice Department would give its blessing. But Google and Yahoo wanted to make sure officials had enough time to review the arrangement, given the questions they had when the companies ran a two-week test of their plan this spring."