London (CNN Business) Facebook built a massive advertising business on what it knows about its users. But could the company's enormous database soon become its biggest problem?

The clearest warning yet came Thursday, when Germany's antitrust office ruled that Facebook was abusing its market position by combining its data with information from Instagram, WhatsApp and third party websites.

The regulator ordered Facebook to stop the practice in a ruling that experts say could shape the company's future — and potentially even lead to its breakup.

"In many ways, they are internally breaking up Facebook by limiting how they do business, how the different services interact," said Anu Bradford, a professor at Columbia Law School. "It's not a breakup, but it is certainly ramping up the pressure," she added.

In many ways, they are internally breaking up Facebook by limiting how they do business." Anu Bradford

The fact that the data issue was handled by an antitrust regulator, rather than a privacy watchdog, could mark an important shift in the way authorities view social media.

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