How did Facebook, Google, Apple, and Amazon get so big (and who let them)?

The rise of global technology superstars like Amazon, Apple, Facebook and Google created new challenges for the competition watchdogs who enforce the nation’s antitrust laws. Those companies dominate markets in e-books and smartphones, search advertising and social-media traffic, spurring a global debate over whether it’s time to rein in such winner-take-all companies. The U.S. has largely been hands off, but that may be changing.

1. Are the tech giants monopolies?

They’re powerful, for sure. Google and Facebook Inc. together control almost 60 per cent of digital ad revenue in the U.S. and 64 per cent of mobile ad revenue, according to eMarketer. Apple Inc. has about 45 per cent of the U.S. smartphone market. About 47 per cent of all U.S. e-commerce sales go through Amazon.com Inc.