Big data, which is one of the main topics of personal data protection law, has become a frequently discussed sub-heading of competition law in recent years. Big data, which is explained with certain criteria such as volume, velocity, variety, veracity and value rather than a clear definition, is a whole of structured or unstructured data with a very wide scope in general terms. Although the first reason that comes to mind in the characterisation of big data is the excessive amount of data, the amount of data is not the only factor. The term big data refers to data that is too large in quantity, speed or complexity to be processed by traditional methods. Big data, which is utilised in many different fields, also plays an important role in making the right decisions and strategic moves in business life. When companies with big data are approached individually, it is realised that they have made significant progress by making use of big data, but when they are evaluated together with companies that do not have the opportunity in question, it is seen that significant drawbacks arise in terms of competition law.

With the use of data as a commodity in commercial life, big data has become an object of competition in itself. Especially with digitalisation, existing data collecting companies in the market create their corporate strategies and new business models based on big data. While this situation brings high turnover and great progress for these companies, it brings up the formation of a dominant position that prevents competition for companies that do not have access to big data.

The fact that companies with big data do not share this resource with other similarly positioned companies within the market or share it only with certain selected partners may create a situation that prevents entry into the market. As mentioned above, market dominance, which can also be considered as monopolisation of data-oriented undertakings, is not only related to the amount of data possessed. The existence of market dominance, which depends on different criteria besides the amount of data, can be determined by answering the following questions:

• Is it possible for other competitor undertakings to access the same data?
• Is there any other data that can be substituted for the data held by the dominant undertaking?
• Does the dominant undertaking have the ability to analyse the data collected?
• Is the data held by the controlling company processed data or unprocessed data?

In particular, data-oriented products such as social media, shopping and brokerage websites require the use of large amounts of data, and the possession of this data by only one or a certain number of undertakings and making it difficult for other undertakings to access it will create the situation of abuse of dominant position identified within the scope of the above questions. Such big data aggregator companies are generally composed of two or more two-way platforms, which, on the one hand, provide free services to the user and, on the other hand, earn income from the data they collect from their users. Although the mere service activity does not involve any unlawfulness, this activity process and its impact on other undertakings may cause violations in the field of competition law. The Bundeskartelamt – Facebook investigation is one of the main and important examples in this regard. Facebook is a very difficult actor to compete in the market with other social networking applications. Facebook retains its users by taking advantage of their fear of losing their connections, and retains the advertisers it cooperates with thanks to the customer potential created by its large user base. In other words, Facebook, which does not have any other enterprise that can compete with the data it possesses, is selected among the options that are not available in practice by utilising its large data source. The fact that Facebook, which provides a social networking service, requests the processing of personal data in return for the service it provides to its users does not constitute any violation of the law. However, the fact that the service provided is subject to the conditions of personal data sharing and processing reveals that the explicit consent condition required for the processing of personal data in both national and international legislation is not duly provided. The German Federal Court analysed this consent condition imposed by Facebook based on the Impact Theory on the grounds that it is unlawful and that this contradiction has an impact on the German market. Within the scope of the review, it was stated that the user consents obtained by Facebook, which is in a dominant position, are not a declaration of a healthy will and do not provide the principle of voluntariness. As a result of the investigation, the German Federal Court issued a ban on the data processing policy applied in Germany on the grounds that Facebook, on the one hand, caused a violation of competition law by preventing users and advertisers from other options with its dominant position, and on the other hand, it obliged users to share personal data.

Personal data/personal data law, which does not even have a long history of its own emergence, has gone beyond its field with digitalisation and innovations, and has started to affect commercial and therefore competition law. The relationship between personal data and competition law is particularly addressed in the context of big data and constitutes the basis for important discussions. In data-driven markets where personal data constitutes the raw material of competition, data collecting companies such as Amazon, Google and Facebook have a dominant position in the market in which they operate with the big data they hold, making competition difficult. The Facebook investigation described above constitutes an important example to understand the perspective that should be taken towards the issue.