I'm planning a new website in which most of the content will only be viewable to registered and logged in users. I would love to keep this site free for my users but wish to defray some of my costs in some way. I have used Adsense on a couple other sites and am fairly pleased with results. However, these sites are the kind where the content is available to all viewers.
Has anyone had success (or otherwise) using Adsense on sites requiring login?
Can adsense even display approriate ads since Google will not be able to index those pages requiring login?
Is adsense even appropriate for a site that will primarily have repeat visitors?
Is there another solution that could help defray some costs but still help keep the site free for users?