The Four Horsemen of Publishing
Viktor Vasnetov's "Four Horsemen of the Apocalypse"
When publishers refer to The Four Horsemen, they usually mean Amazon, Apple, Facebook, and Google.
The concept of publishers having to joust with the fearsome, well-financed Four Horsemen started in the book-publishing industry. But the allegory is easily grasped by all publishers who warily view these web giants as, at best, frenemies.