If you want to know how synergistic the Microsoft-Yahoo merger would be (and if, somehow, you have forgotten the giant disaster that was the Time Warner-AOL merger), you have no farther to look than Google's success with even tiny acquisitions.
Like say, JotSpot.
Which, after being bought by Google, had exactly zero visible improvements made to it, until today, when there was a rather visible change: it dropped off the net.
Instead, there's a Network Solutions domain capture page.
Not surprisingly, there is some consternation in the JotSpot Help group http://groups.google.com/group/jotspot-help This is a good reminder about the risks of living "in the cloud" (I have quite a lot of work put into pages in my JotSpot wiki, they had better be coming back online).
UPDATE: Someone somewhere pushed the right button and the wikis are back. Needless to say I will be saving copies of my private pages (the public ones at least would have been recoverable in Google search cache).