I looked into jumping into this space recently, and doing my research it seems that all the companies doing this exact same thing (and there are lots of them) make the same mistake that this one does: Involve the customer in the loop.

This requires Joe AirBnB User to actually sign up for an account with the service (and a dozen others) and tell it about all the places that it should agglomerate reputation from. That's precisely backward.

This service's customer should be AirBnB, eBay, etc. And if the big ones don't immediately sign up, you'll need to go convince (as in, pay) them to partner up from the start. Customers get matched up with profiles behind the scenes automatically and end up with a "credit score" assigned to them that they have no control over.

The company that builds that product will win. The other twenty will die, as they are currently in the process of dying, because nobody is going to wake up in the morning, Google "centralized trust service", sign up, and spend an hour filling in information.