The way the question is worded, it seems to me that you have a product idea which you want validated. I'd be wary of this method of building sideprojects becaus

The way the question is worded, it seems to me that you have a product idea which you want validated. I'd be wary of this method of building sideprojects because it will close you off to other, possibly better ways of achieving your end goal. /metaAnswer If you look at this idea with squint eyes, in a way, it has already been implemented. Facebook and Google show you posts you are likelier to read ("trust") because of all the profile information they have on you. Each Like and Share you do raises that article's "trust" score. Will you be able to become the Verisign of trust? Maybe. Verisign's business is built around maths. What are you going to build your "Trust" number on?