"The value of advertising online ought to be measured more by
engagement than by sheer numbers, that is, more by metrics like time
spent or page views per user than by the sheer number of people coming
to the site, many of whom may not assign any value to the journalists
who generated the content.
"Indeed, as we hear more about “freemium” (mixed paid and free)
models, publishers and editors ought to be thinking about who their
most engaged readers are and what characteristics they share."
— From "Yes, News Sites Are Facing A Crisis, But Aggregators Aren't The Problem," by Bill Grueskin, Columbia University, in paidContent.org