Magazines (fashion, fitness, sport, etc) have this effect by virtue of advertisers not wanting to be seen in a "free" publication, but most of their revenue still comes from ads, which is why you continue to still receive new issues for months after you supposedly canceled, even though you nominally are paying for it, all the incentives are for them to pretend you're a paying customer when you in fact are not.

But I don't really know how you could reasonably make this work for online communities. Is reading a blog and commenting on it participating in a "social network"? What about reading a blog without comments? Viewing a sponsored Twitch stream?