We don't have the tech for two important, related things: user-friendly, trust management tools as effective as in person; key management for various, complex scenarios. These two have so many issues that even technical people screw up. I've certainly seen a lot of good work on these. Yet, we're not there yet and getting there is worth a ton of effort by anyone who will try.
We get that, then we might integrate it with our existing technologies to implement and use it. Need the foundation first, though.