Between June and September 2019, the European Commission has approached and questioned several (online) market players in the context of its investigation into (the advertising services of) Facebook. Diederik Schrijvershof and Wouter Jans represented a market player regarding the European Commission’s investigation into Facebook.
In response to the complaints from various competitors of Facebook, the European Commission is examining the possible anti-competitive effects of Facebook’s position on the market for online advertisement services.
See here and here for more information on the European Commission’s investigation.