Businesses need advertising, especially small and medium sized enterprises selling niche products to reach out to prospects and retain customers. Yet, there is a tendency at national level to challenge data marketing and legitimate interest (LI), a necessary legal ground for all sectors. Indeed, some Data Protection Authorities (DPAs) are encouraging the use of consent over legitimate interest (e.g. through guidelines) while some are excluding the use of LI. This article focuses on the first GDPR fine imposed in the Netherlands which concerns KNLTB, the Dutch national tennis association, responsible for all professional and leisure tennis in the Netherlands. Although the facts of the case seem simple and straightforward, the Dutch authority(1) pronounced a heavy fine for two GDPR violations: incompatible processing and processing with lack of a legal ground. The decision clearly excludes the use of LI for monetizing data by making it available to third parties for advertising, jeopardizing the future of data marketing.