App makers periodically allege that they are blocked because Apple wants people to use its own services. In a recent example, several makers of apps for managing the amount of time kids can use their iPhones say they were kicked out of the store not long after Apple introduced its own screen-management controls.
Apple says it typically blocks only apps with buggy software or features that invade users' privacy. The company likens its rules to merchants deciding what products to carry. Apple also says its store includes apps that compete with its own products, including Google Maps and Google's Chrome browser.
Also under criticism is the 30% cut that Apple pockets on new subscription sign-ups during the first year and a 15% slice for renewals. The app store is expected to generate about $16 billion in revenue this year.
Apple says the commissions cover costs for running the app store, including hiring people to review apps.
Antitrust regulators could try to impose requirements that lower Apple's commissions or, in a worst-case scenario, force it to spin off the app store. The latter option, though, could hurt consumers by making iPhones and other Apple products more cumbersome to use.
Wedbush Securities analyst Daniel Ives likened a breakup to "a complex and almost impossible Siamese twin operation."
Amazon
The only one of the major tech companies not based in the Bay Area, Amazon has grown from an online bookseller into a gigantic e-commerce player with its tentacles in everything from web hosting to streaming video to groceries.
The European Union's antitrust chief has been conducting an early-stage probe into whether Amazon is using data to gain an edge on third-party merchants, who are both its customers and rivals. Italy has been looking into whether Amazon abused its dominance by offering preferential treatment to companies that used Amazon's own delivery-management services.
Cicilline, the congressman, said Amazon has identified bestselling products elsewhere, rolled out replicas under its own brand and then steered customers to its own products over those of its rivals.
When Warren tweeted in April that big tech companies like Amazon should be broken up, Amazon tweeted back: "Walmart is much larger."