Google in particular. What makes a monopoly dangerous is when they control multiple links in the supply chain to push out competitors.

If Google owns Search, Gmail, Android, Analytics, Chat, Google Fi, Google Fiber, Chrome, GPay, etc... then they are able leverage one monopoly to establish monopolies elsewhere.

...and that is ultimately what is most destructive to Competition and consumer value. All of the above could be separate companies. Facebook gets a lot of bad press, but Google is the big danger.