Facebook's vast data stockpile has caught the eye of competition officials in Germany, who have opened an investigation into claims that the company may have abused its dominant position in the social network market.

On Wednesday, the Bundeskartellamt (literally the "Federal Cartel Office") said that it was mulling whether Facebook had taken advantage of its market power by violating data protection rules. It's unusual for an antitrust watchdog to conduct proceedings that cite concerns about data-hoarding, Germany's cartel office noted. Facebook appears to be an exception, however.

"Dominant companies are subject to special obligations. These include the use of adequate terms of service as far as these are relevant to the market," said the Bundeskartellamt's president, Andreas Mundt. "For advertising-financed Internet services such as Facebook, user data are hugely important. For this reason, it is essential to also examine under the aspect of abuse of market power whether the consumers are sufficiently informed about the type, and extent of data collected."

The German regulator added that it was working closely with other competition authorities in the European Union, consumer protection groups, and Brussels' antitrust officials as part of its probe.

Facebook has, in recent months, undergone intense scrutiny from watchdogs in Europe. Dutch, Spanish, French, and Belgian data authorities have—alongside German regulators—been poking around Facebook's business practices, as part of a pan-EU probe to tackle the company's huge data-hoarding practices.

Last week, Zuckerberg went on something of a charm offensive in Berlin when Facebook announced that it was donating 25-GPU based servers to Europe to help bolster AI research.

When quizzed by Ars about Germany's competition probe, a Facebook spokesperson said: "We are confident that we comply with the law, and we look forward to working with the federal cartel office to answer its questions."