I worked for a company that would have been a target client for a product like this. In the end, we didn't use one of the many similar solutions (legit.co, trustcloud, scaffold, peertrust, project trust, truly, etc..) for two reasons:

* We didn't want to give our information away. It was a nonstarter. Either to protect it from being used by competitors or because of security concerns of giving private user information to a third party. * Each site and community has different levels of trust, and actions have different meanings. Whether someone commits sexual harassment on OkCupid doesn't matter when you are trying to buy their toaster on eBay. I am much more concerned about someones behavior when they are living in my house, not so much when they are giving me a ride in their car within the city at noon.

It would be nice if everyone didn't have to build their own trust system, but any competent company will. A general solution will either be too general to be useful, or require too much private information to be allowable.

The only way I can see a standalone product like this occurring is if a well established company like AirBnB of Facebook would build it on their existing (valuable) dataset and and guarantee data privacy.