Earlier this summer Google and Yahoo announced that they will be working together to offer online ads for Canada and US users. Since the two companies, between them, rule of the online advertising business this was big news. They announced then that they will not move to implement the agreement right away but will wait for the government regulators to decide upon this. A few days ago Google announced that they are canceling the agreement.
Google decided to cancel the agreement because as they said some regulators and advertisers continue to have concerns about the agreement. What this, basically, means is that "it would be nice to work with yahoo and create an online advertizing cartel but it would be even nicer not go into a lengthy and costly battle against the government or other online advertisers". I do not blame them and in fact as a consumer I feel relieved that that there is one less cartel in the market to rule a part of the business.
As they have stated:
If this ended in legal battle it would cost Google a great deal of money and would possibly hurt its public image as a company.
We're of course disappointed that this deal won't be moving ahead. But we're not going to let the prospect of a lengthy legal battle distract us from our core mission. That would be like trying to drive down the road of innovation with the parking brake on. Google's continued success depends on staying focused on what we do best: creating useful products for our users and partners.