Cash, Paranoia Fuel Tech Giants' Buying Binge

From messaging to watches and thermostats, Facebook and Google, along with Amazon and Apple, each want to own the digital platform where people communicate, shop and seek entertainment. The competition is driven by their ability to pay -- their combined market capitalization exceeds $1 trillion -- and long memories of faded tech stars that didn't evolve quickly enough.

This combination of fear and primal ambition is leading to one of the biggest buying and investing sprees since the dot-com era of the late 1990s. Facebook and Google, in particular, have enjoyed wide latitude to make big investments, thanks to their booming stock price and their founders' supervoting shares. The four companies are competing to control as much as possible of the tech ecosystem. In Silicon Valley parlance, it's all about controlling "the platform." A big reason is to gather data about users, to serve them ads or to anticipate their next purchase.