Free sharing is everywhere on the Internet. In the non-commercial sphere it corresponds quite naturally to a gift and counter-gift logic; in the commercial sphere it is more difficult to interpret. This article examines the role of free sharing in commercial activities on the Internet. We show that it cannot be reduced to a classical media model, based on the audience's valorization, but fits into a broader process of co-production of commercial services. In order to construct economically viable business models, most commercial actors on the Internet rely on free sharing of information, especially on Internauts' propensity to offer opinions and advice free of charge.