I absolutely loathe the introduction of the paid DMing. While I can understand that some people aren't as well off, and would like to create a way for themselves to pay for books-modules-maps-tokens so they can be a better DM, too many people use it to actually make money, and I feel it spits in the face of the spirit of D&D. My mini-rant aside, as a firm believer in capitalism, there needs to be a way to ensure that the market can weed out lousy service providers(DMs). That's why I suggest that there be a ranking system, akin to Angi's List or Yelp... Where Roll20 users can anonymously rate and comment on DMs and players alike.