Online platforms, which are at the forefront of today's economy, are subject to intensive competition law enforcement. However, the platform business model presents challenges for the application of competition law. Most notably, they appear to offer consumers a great number of their products for free. The explanation for most of these supposedly free products is offered by two-sided market theory: consumers may not be paying, but the 'other' side of the market is. This other side of the market often consists of advertisers, which pay the platform for access to the consumers' information (to target advertisements) and attention (to show the advertisements). As many of these platforms are now potentially dominant, they come within the scope of competition law's abuse of dominance provision, including the doctrines of predatory and excessive pricing. These price-based theories need to adapt to the often price-less platform business model in order to prevent competition authorities from making both type I and type II enforcement errors. At the same time, competition law enforcement needs to consider-and at times give priority to-other branches of law that address abusive behaviour concerning free products. Through the use of case studies, this article therefore suggests ways in which abuse of dominance assessments can take into account the economic reality of free products.

The need for online platform regulation has been a topic of scholarly debate. However, reality is now catching up to and even overtaking the academic writing on this subject. France has adopted a law on platform fairness, the European Commission recently ordered Google to implement a form of search neutrality, and more regulatory initiatives are on the horizon. That is why we have to look beyond the question whether online platforms should be regulated. As actual regulation supplants the scholarly debate, we must also examine how they are being regulated. This article distils from the various proposals at EU and member state level a set of operational principles that can serve as a frame of reference for productive debate on platform regulation.

When competition authorities struggle to assess abusive practices by online multi-sided platforms, the issue does not appear to be defining markets or determining market power; rather, the difficulty is finding a fitting theory of abuse. In the search for such theories, one candidate has been overlooked: margin squeeze. This class of abuse has for the most part been confined to the telecom sector, but its potential reaches beyond. Indeed, the tendency towards vertical integration and subsequent conduct of online platforms could renew the relevance of margin squeeze as an analytical tool. To test this relevance, the article first examines the foundations of margin squeeze theory, while also addressing possible misconceptions. It then investigates whether this theory could be applied to online platforms with the help of three case studies (involving app stores, search engines and online marketplaces). Where a company not only owns the digital infrastructure but also uses it to provide products, we find that margin squeeze can provide an appropriate assessment framework for anti-competitive conduct. Before concluding, the article contemplates the idea of neutrality underlying margin squeeze and related policies such as network neutrality.

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