It's funny, but the moment I read about the fair use amount, I pictured hundreds of scanners all posting a tiny, legal amount in order to put up entire comic books. We could become a link roundup.
..Anyway, the standard isn't 'is it useful for you to come here'. Also, the previews get taken down so they're not useful as a resource unless you're only using them as previews. The major thing that annoys creators (besides putting up whole stories like was done with Colleen Doran's stuff) is the spoiler pages, which are arguably the essence of the book. Nobody cares if we do that to 6 month old books. It's the new books we have to be careful of.