The concept is a service-independent website where users can document what media they were unable to find on what services. For example, a user might list the films they're frustrated aren't on Netflix or Hulu. And then other users can vote on these requests, such that the most significant gaps in content become most obvious.
The service would be a bonus for the online media services as: it would link into their libraries such that when a person reports "I can't find X on Netflix" the system tells them "Don't worry, it's on Hulu". And similarly, when the online media services do finally get the content, the website can update the request and put a link out to the site.
The concept applies across all kinds of online media services, but would be particularly relevant to the mainstream services covering TV, music and film.
The service would be relatively easy to build, as many online information sites (e.g. IMDB) provide APIs to allow details of the media content to be pulled in.
It may be necessary to make the documentation of gaps and voting region-specific due to the regional specificity of some online media services.