Perhaps most important, putting content behind a pay wall robs it of precious Google juice. Even if Google can search it, the hidden content will not attract as many of the links and clicks that Google's search watches and values. In American newspapers' sites, as few as 20% of users in a day come through the home page; most come to news via search and links from aggregators, bloggers, feeds and Facebook. Cutting yourself off from that rich economy of search and links is like taking your publication off the newsstand and making your readers walk to your office to buy it.
