Excellent analysis and input so far!
I have to add that I've experienced the opposite: if I post a new video to ElliNude.com, the ones I post with trailers/samples sell far better than ones without the samples. Maybe people aren't sure what quality to expect, or something. I don't give away the "good stuff" in the trailer, though, and I censor anything hardcore (genitals, etc). Maybe the censor blocks work like for GGW?
Who knows? that's been my experience, at least.