U.S. tech giants might have a respite after two decades of European Union antitrust investigations. But not for long.

While Google (GOOGL.O) just got a third, and possibly final, EU fine on Wednesday, regulators still have their eyes on Amazon.com Inc. (AMZN.O), Apple Inc. (AAPL.O) and Facebook Inc (FB.O).

EU antitrust chief, Margrethe Vestager, told reporters earlier this month that an early-stage probe into Amazon’s potential use of data to overtake smaller shops on its Marketplace platform is "quite advanced" and she’d "like to take more decisive steps" before she leaves office later this year. That might see the start of a full-blown investigation.

She’s also promised to examine a complaint Spotify Technology SA made targeting Apple’s app store and has said she "takes an interest" in potential anti-competitive behavior by Facebook.

There are new cops doing the rounds too -- privacy authorities in countries armed with the power to levy fines of as much as 4 per cent of a company’s annual sales for breaching the EU’s new data rules.

‘The truth is that many regard Google and Facebook as out of control,” Jonathan Compton, a partner at DMH Stallard in the U.K., said in an email after Wednesday’s fine. “The deeper problem is what to do about it. Even if you make the decision to regulate the big platforms, and that is an issue in itself involving freedom of expression, how can those platforms regulate their content when they have two billion or so users?”

Ireland’s data protection commissioner Helen Dixon is already looking into at least seven privacy probes targeting Facebook, with several other investigations her office opened targeting “very big internet companies,” she said in an interview in February. France’s data watchdog in January levied a record 50 million-euro fine against Google, which showed that watchdogs are taking the new guidelines seriously.

New regulatory risks for tech companies are emerging. The EU agreed to new rules for online platforms in February that require internet firms to address some issues that have triggered antitrust cases. They will have to provide clear terms of service, more transparency about how products are ranked, and to establish a system for handling complaints. Companies are also required under the new rules to "exhaustively disclose" any advantage they give their own products.

A copyright reform finalized last month forces web firms to compensate publishers and creators for the content that appears on their websites. At the same time EU regulators are demanding Twitter Inc., Facebook and Google do more to fight disinformation on the internet ahead of May elections.