As companies such as Facebook, Amazon, Alphabet (the parent company of Google) and Apple buy out their competitors and maintain well-over the majority of the market-share in their respective industries, do we need to be concerned that these companies are well on their way to becoming monopolies?
Monopolies are made through acquisition; here are a few examples:
Google acquired AdMob and Double-Click
Amazon acquired Audible, Twitch, Zappos, and Alexa
Facebook acquired Instagram, WhatsApp
A breakdown of market share ownership:
"They're all tech companies, and each dominates its corner of the industry: Google has an 88 percent market share in search advertising, Facebook (and its subsidiaries Instagram, WhatsApp, and Messenger) own 77 percent of mobile social traffic and Amazon has a 74 percent share in the e-book market. In classic economic terms, all three are monopolies." - Jonathan Taplin, Director Emeritus, University of Southern California's Annenburg Innovation Lab