As if Yahoo didn't have enough uncertainty to contend with right now, three of the largest newspaper chains in the country have launched a new company called QuadrantOne, which may both compete and overlap with Yahoo's online ad network.

Spearheaded by the Hearst, New York Times Corp., Tribune, and Gannett newspaper companies, QuadrantOne will reportedly focus on selling display advertising, one of the very strengths Yahoo is touting for itself in an attempt to ward off acquisition by Microsoft.

Generally speaking, these and other ad networks offer "joint buys" across media properties, to lure big advertisers who might otherwise be deterred from advertising in small or local online publications by the difficulties of negotiating multiple individual deals.

At least one of the members of QuadrantOne, Hearst, is also a member of Yahoo's online ad network.

Yahoo's ad network also encompasses Cox, Media News, and about 15 other newspaper chains.

Further, Yahoo negotiates large advertising deals with other types of companies, too, such as Comcast, the biggest cable TV provider in the US.

Meanwhile, the three founding members of QuadrantOne reportedly plan to try to recruit other newspaper chains to join in with them in their new, competing ad network.