Mobiles may matter more than the desktop
Since the PC browser search and ad experience have been dominated by Google, Microsoft's competitive play may be on the mobile side, where no single provider dominates search.
Picking off Yahoo during a low point in its market performance would give Microsoft a significant boost to its online fortunes. Microsoft's share of the search market triples if the takeover succeeds, and paid search ad revenue should increase.
The cynical viewpoints we have witnessed online about competitors in other industries teaming up to take down a market leader, and failing in spectacular fashion, suggests Microsoft may opt for a softer target to establish itself as the go-to destination.
Millions of mobile phones nestle in the pockets and pocketbooks of people around the globe. Microsoft already occupies the desktops of millions of people, even if those folks promptly head to Google after booting Windows.