Great post from Rich Skrenta about Winner-Take-All: Google and the Third Age of Computing. To his initial chart I would add a third column reflecting what they were monetizing:

• IBM sold you hardware in exchange for money.
• Microsoft sold software you software in exchange for money.
• Google gives you stuff for free, but sells your attention to advertisers. (Using the mechanisms I explained in Attention to dollars, and other exchanges)

Note that both IBM and Microsoft were selling "stuff", even if the stuff was just an arrangement of 1's and 0's as in Microsoft's case. To borrow a page from Goldhaber, now that "stuff" is so easy for people to get, the real economy is in attention--the one thing which cannot be commoditized or pirated or open-sourced.