The Microsoft-Yahoo soap opera has entered a new phase. And in the latest episode, special guest Google has entered the scene.

Yahoo has done a deal with Google to run Google ads alongside Yahoo search results in North America. This is a non-exclusive deal which Yahoo could repeat with other ad providers if it wanted.

The deal with Microsoft's biggest rival looks like a deliberate snub. On Thursday, Microsoft said it wouldn't buy all of Yahoo, but it might just be interested in buying a part, such as the search business.

Yahoo immediately dismissed this idea as out of the question and pronounced all talks with Microsoft over.

Remember this all dates back to January 2008 when Microsoft offered to pay $40 a share for Yahoo. The Yahoo board rejected the offer and the companies have been in on-off negotiations ever since.

Meanwhile, shareholder activist and billionaire investor Carl Icahn has been lobbying for Yahoo chief executive Jerry Yang and the Yahoo board to quit and for other shareholders to embrace the deal with Microsoft.

What Icahn's next scene will be is anybody's guess.

Here's the story so far …