Google's search deal with Yahoo might be a boon for both companies, but the agreement, which has yet to take effect, has many advertisers worried that keyword prices will increase.

According to Advertising Age, concern among search marketers that the deal will lead to higher keyword prices appears widespread.

But Google, which has been adamant about working with regulators to address antitrust concerns, insists that its auction-based system will mean that the market, not the search engine, will set the price. However, that assertion isn't holding water with advertisers, who point out that Yahoo prices are typically lower than Google's. At the very least, that fact has many worried that Yahoo prices will rise to meet Google's.

Discontent among advertisers may also lead to increased regulatory scrutiny, at least abroad. The Independent is reporting that U.K.-based advertisers are calling on their government to investigate what they claim is a monopoly on search by Google. Here in the U.S., Sen. Herb Kohl, D-Wis., has also vowed to scrutinize the deal. But Kohl hasn't set a timetable for the Senate's antitrust subcommittee, which he chairs, to hear the matter.   

As for the Yahoo side of the deal, that company hasn't exactly impressed the space either. The New York Times blasted Yahoo boss Jerry Yang, calling him a "pawn of the most dominant company on the internet."

But the deal isn't without merit, according to Carl Icahn, the activist investor who has taken on Yang in a bid to restart talks with Microsoft. While the Microsoft talks are now dead, Reuters is reporting that Icahn, who has launched a proxy fight for control of Yahoo, is in something of a holding pattern. However, Icahn wouldn't comment on whether or not the proxy battle would continue.