News reports this week that the U.S. Department of Justice is formally reviewing a proposed advertising deal between Google and Yahoo came as no surprise to some tech trade groups and advocacy groups based in Washington, D.C.

A Washington Post story Wednesday saying the DOJ had launched a formal investigation of the ad deal wasn't much of a shocker to Google and Yahoo, either, as the two companies had voluntarily delayed the implementation of the deal for more than three months in recognition that the DOJ would look at the antitrust implications.

A DOJ spokeswoman said Wednesday that the agency has acknowledged since mid-June that it was looking into the deal. A public confirmation that the DOJ is examining the deal amounts to a "formal investigation," she said.

Google said it is cooperating with the DOJ.

"We are continuing to have cooperative discussions with the Department of Justice about this arrangement, and voluntarily delayed implementation for three and a half months in order to give them time to understand the agreement," said Adam Kovacevich, a Google spokesman. "That process is continuing exactly as expected. We are confident that the arrangement is beneficial to competition, but we are not going to discuss the details of the process."

Google and Yahoo announced June 12 a deal to run some of Google's advertisements alongside Yahoo search results. The announcement came just hours after a proposed acquisition of Yahoo by Microsoft fell through, although Microsoft has continued to express interest in such a deal.

Google and Yahoo had run a test of the advertising program in April.

Still, with recent news of the DOJ investigation, representatives of two tech trade groups said they expected the agency would look into the deal.

"Even though serious antitrust problems are unlikely, it was appropriate for the parties to offer up a delay while regulators review the deal," said Ed Black, CEO of the Computer and Communications Industry Association, a trade group that has raised concerns about anticompetitive behavior in the tech industry. "This is a good provision to help everyone understand the facts surrounding the deal and make sure there is no harmful impact on competition or consumers."

A formal review was "inevitable," added Jonathan Zuck, president of the Association for Competitive Technology, a trade group often aligned with Google competitor Microsoft. The deal is between the number one and number two companies in the "crucial" online ad market, Zuck added.

"It's a very complex deal in a very complex market," Zuck said. "The deal raises a lot of questions that the DOJ must answer before letting it go."