We experimentally investigate the willingness to sell highly sensitive personal data from different social networks. To analyze the perceived loss of selling data, we have sequential selling decisions in which we vary between researchers and external firms as buyers, and we vary the number of buyers. In particular, we are interested in (i) whether our participants are more willing to sell additional data sets if they have already sold data to the same buyer, (ii) whether the willingness to sell differs depending on the type of buyer, and (iii) whether the willingness to sell differs for alternating buyers. We link our analysis to current debates in competition economics. We further collect information about personality traits to investigate sellers’ heterogeneity.