It's the end of the world as advertisers know it. If that seems like an exaggeration, consider what one Publicis Groupe executive told The Wall Street Journal in reference to the fast-exploding Microhoo mess: "The flurry of news over the last 18 hours is the online media industry's equivalent of nuclear war. Nothing short of a new world order in this space is up for grabs."

Since Yahoo's bombshell news earlier this week that it planned to test Google's AdSense on 3 percent of its U.S. search traffic, virtually every major player in the online advertising business has been swept up into the vortex.

Rupert Murdoch has allied his News Corp. business with Microsoft, which screamed about antitrust concerns shortly after Yahoo looked to Google for help. But at the same time, AOL, which long since outsourced its search to Google, has been rumored to be in talks with Yahoo about a possible merger. But that news has been topped by today's revelation that Google has hired investment banker Frank P. Quattrone to advise it through what promises to be the mother of all digital upheavals.

For those keeping score at home, the battle lines now look like this: in the middle stands Yahoo, a slumping internet giant that has been telling anyone who will listen that it will soon turn the corner as advertising dollars pour into emerging platforms such as social networking, mobile and video. To bolster its claims, Yahoo has been working feverishly to launch -- or at least announce -- a slew of new products.

Microsoft
At the gates stands Microsoft, which Yahoo seems content to cast in the role of a barbarian since its decision to make an unsolicited bid for the company. For the past two months, many have seen the Yahoo/Microsoft posturing as being largely about money. But in the past week, what looked like an imminent deal turned personal, and now some wonder if Jerry Yang and Microsoft boss Steve Ballmer could possibly be able to bury the hatchet and make a combined company work should a merger actually happen.

News Corp.
Allied with Microsoft is News Corp, which seems to be betting that the combination of Microsoft, Yahoo and digital assets that include MySpace could be a serious rival for Google as social networking and mobile become more important. Presently, Google has a deal to sell ads on MySpace, but the search giant has publicly blasted the site as being difficult to monetize, and both sides seem to be keen to find a way out of that agreement. However, a combined Microsoft/News Corp. acquisition of Yahoo would put both MySpace and Facebook under the same umbrella because Microsoft beat Google to the punch when it bought a stake in that social network.

AOL
Sitting squarely on Yahoo's side is AOL, but the company could hardly be described as a white knight as it struggles to find its way into the advertising business. But one asset it does bring to the table is Bebo. Last month, AOL bought the British social network, which is a distant third behind MySpace and Facebook.  

Google
Comfortably atop the fray sits Google, which probably won't be able to offer more than an AdSense agreement to Yahoo. However, the company is said to be keeping its options open, which seems to be no surprise given the dynamically shifting landscape. In the meantime, it continues to use the distraction to its advantage as it works to integrate DoubleClick into its empire.

The player nobody wants to see
Throughout this two-month ordeal, there has been little talk of government regulation. Analysts have been keen to point out that Microsoft would need regulatory approval if it is to buy Yahoo, but now it seems that Congress could get involved no matter the outcome. Yesterday, House Judiciary Committee Chairman John Conyers, Jr. (D-MI) and Ranking Member Lamar Smith (R-TX) issued a joint statement saying the news "further underscore[s] the need for a hearing on the state of competition on the internet and online advertising."