I'll admit that I haven't used the Marketplace much (yet), but including the ability to rate content seems like a no-brainer. People have enough drains on their hard-earned money, without getting sucked into paying for poor-quality content in their RPG products. Likewise, people who create quality content should be rewarded and encouraged (with positive reviews, which will hopefully lead to greater sales). Just about every other online marketplace includes this feature, I'm baffled as to why Roll20 does not.