ReviewBasics is a feedback gathering platform which allows you to comment and review many types of creative, motion, and written content. The site looks slick, and I can imagine web-designers and designers might use this service to get feedback from their clients on their work. I’m less inclined to believe it will be a hit for written docs as there are many other collaboration tools that are more suitable for gathering feedback.
I’ve seen similar offerings before, but think ReviewBasics is definitely worth a try. Its in open beta, so is free to use presently – no idea what it will cost thereafter.