This almost sounds like something too good to be true. Big companies like Twitter and Facebook wouldn't want to use this service because they want to collect the data. This company would need to charge websites for the service, otherwise their only alternative is to sell their user's data or advertise, which leaves us right where we already are.
Of course there may be other ways for such a service to survive, but those are my initial thoughts about seeing something like this happen. I would love for something like this to exist, though
I take the opposite view...something like this seems rather viable as a business that companies would gladly pay money for but it also basically sounds like another Equifax/Experian/Transunion fiasco waiting to happen. The only logical thing I can thing of is a consortium of the big telcos creating a shared database and service that companies could tap into.
Of course there may be other ways for such a service to survive, but those are my initial thoughts about seeing something like this happen. I would love for something like this to exist, though