If they could strike that kind of relationship and convince the Department of Justice that Yahoo! was no longer a top search provider since it has outsourced all its back-end search talent and technology to Microsoft, it could be a powerful relationship between Google and Yahoo!.
Any one of these kind of partnerships would be a home run for Yahoo!, assuming there really was teeth to the deal which led to real results for Yahoo's shareholders.
Mayer is right that it is conceivable that she could partner with any of these companies. But can she partner with all of these companies simultaneously? Almost certainly not.
There will come a time where Mayer has to bet on one of these horses in a big way. When she does, she will have to ride that horse -- unless of course one of the spurned companies comes back and tries to buy Yahoo to keep them away from their competitor.
We're coming up to a key decision point at the end of March, when Mayer will decide Yahoo!'s future in search.
Kara Swisher has recently said Mayer was actively looking at ways to end the Microsoft relationship in search. That's pretty big news if it happens. I remember tweeting with Swisher on that possibility last summer and Kara thinking it would be highly unlikely. Indeed, it might still be.
There is no question though that Yahoo! could make more money from search by teaming up with Google over Microsoft. I think there's also a good line of reasoning to argue to the DOJ why a partnership doesn't run afoul of antitrust concerns.
However, many observers like Swisher and Danny Sullivan of
Search Engine Land
have long argued that it would be much easier for Yahoo! to simply re-up a deal with Microsoft on better terms if necessary.
Their reason for saying this is primarily because, after signing the 2009 deal outsourcing search to Redmond, you can't go home again. It would be very difficult to re-start a search business from scratch, which is what Mayer would be signing up for. Better instead, this thinking goes, to just play nice with the devil you know.