Google surpassing Yahoo as most visited US site; but Google-Yahoo don't really compete do they?

As Google and Yahoo continue to negotiate their search outsourcing pact, pesky competitive facts keep arising that suggest that such a deal is likely to eventually be found by antitrust officials to be illegal anti-competitive collusion.

• Yahoo is running an AP story that says that Google has now surpassed Yahoo as the #1 "most popular website in the United States according to Comscore."
• This is on top of Google and Yahoo being the #1 and #2 search providers in the U.S. and the leading competitors in the display advertising market, ad tools market and ad brokering market.

The operative question is not whether Google and Yahoo can craft an acceptable search advertising outsourcing pact that can pass antitrust muster, but whether the DOJ wants to encourage such intimate  and important business "cooperation" between Google, the dominant #1 in the market, and one of the only two companies that most consider to be Google's primary competition in multiple market segments.