When you look at the cultural differences between Microsoft and Yahoo, you don't need to look much further than a floor plan.
Microsoft has been a company of offices, where workers toil individually at their piece of a collective project. Yahoo, by contrast is a Silicon Valley archetype where workers sit in cubicles and tend to work collaboratively.
The folks in Redmond are known for being hard-charging and competitive, both internally and externally. Yahoo, meanwhile, tends to be more collaborative, sometimes to the point of inefficiency.