Amazon – Classic hierarchical structure, Jeff Bezos sit at the top and drives the ship. Its a typical pyramid shape
Apple – This structure is during the era of Steve Jobs, who used to be in the middle and everyone revolves around him. This changed as well, when Steve Jobs passed away in 2011.
FaceBook – Their model is as per the companies profile – Networking. It looks very much a social network structure.
Google – Much more networked, everyone talks to everyone, except for the three on top. The one in the middle is, the CEO, while the two on the sides are the founders.
Microsoft – This has changed significantly after the Steve Ballmer left. Now the focus is back on the product range.