As Steve Yelvington recently noted,
Pretty much everybody who's talking seriously these days about asking users to pay for news content is pointing at the same model: Leave the website open to casual visitors, but require heavy users to sign up as paying customers.
But as Steve observes elsewhere, this is a tricky proposition. While heavy readers might account for only 2 or 3 percent of a site's total unique users each month, they also account for "20 to 30 percent of the pageviews" – and advertising revenues. If you turn them away you could lose a lot of money.
But this misses the point – or rather fails to see it fully. The more clever strategies out there don't start from the assumption that frequent readers are likelier to pay. They start from the assumption that there are some readers out there who are willing to pay, and that this segment has a large overlap with – but is not necessarily the same as – that of heavy users (see my earlier post on this).
For example, you might find that readers who always arrive via deep links will not be willing to pay, even if they visit frequently. If so, then you would restrict your pay-wall to users who visit frequently and come via the front page. Your billable segment gets smaller, true, but so does your risk of turning away ad-seeing people who won't pay. And you might find that among people who arrive via the front page, less-heavy users might also be willing to pay.
The industry's challenge is not to find out how frequent your readers need to be for you to show them a pay-wall, and how much to charge them. It is to find the right combination of online behaviours (entry points, referring sites, frequency of visits, etc) that serve as proxies for willingness to pay. That's where energies are being concentrated, and where all kinds of secret sauces are being brewed.