Some UK digital ad agencies are already getting nervous about Yahoo’s (NSDQ: YHOO) face-saving deal to display ads from a Google increasingly dominant in the sector. Two examples from a MediaWeek ring-‘round...

SEE ALSO: Yahoo And Google In Non-Exclusive Search Ad Deal; $250-$450 Million Extra Op Cash Flow

—Nigel Gwilliam, digital head, Institute of Practitioners in Advertising: “When the number one and number two search engines join forces, anti-trust alarm bells do start ringing.”

—Oliver Bishop, CEO, Steak agency: “Yahoo has a Google (NSDQ: GOOG) dial that it can now turn up and down regarding the Google ads it chooses to display. Should Yahoo need an influx of revenue, turning that dial up becomes increasingly attractive.”

To avoid a Microsoft (NSDQ: MSFT) acquisition, Yahoo last week agreed to place a number of ads from Google’s inventory on its search pages and some other web properties. The US Department of Justice had already launched an inquiry in to an earlier test of the tie-up, and a Senate antitrust subcommittee has warned that it will investigate, too. Yahoo and Google said they don’t expect regulatory approval, though they will put things on pause for three months to seek the DoJ’s green light. Maybe the UK agencies are getting their knickers in a twist, however - the deal applies only in the US and Canada.