"The article threshold has often been discussed as if it was simply a new method of getting readers to pay, to which the reply has to be “Yes, except for most of them.” Calling article thresholds a “leaky” or “porous” paywall understates the enormity of the change; the metaphor of a leak suggests a mostly intact container that lets out a minority of its contents, but a paper that shares even two pages a month frees a majority of users from any fee at all. By the time the threshold is at 20 pages (a number fast becoming customary) a paper has given up on even trying to charge between 85% and 95% of its readers, and it will only convince a minority of that minority to pay."

Newspapers, Paywalls, and Core Users « Clay Shirky