Yes. It is about trust. Bitcoin create trust through a market. People trust in the market. People trust that someone is going to value a cryptocoin when they want to exchange it. But there are also other ways to create a payment system based on trust.
Trust exists between people. You trust your friends. Your friend trust someone else that in turn trusts someone else. These trust-chains create a possibility to pay a stranger.
The idea was called Ripplepay (and Ripple) before the Ripple crypto currency was created. Many confuse the two ideas. The Ripplepay idea is about creating a fully decentralized payment system without using a market.
Yes absolutely. Bitcoin realises trust by proof of work. Ripple or Stellar use links of trust, where in theory every link should be realised below the Dunbar number. In practice this is very unlikely to work due to liquidity issues and laziness, but since you can choose who to trust, bad actors will be filtered out anyways.
So there are multiple options for solving trust available right now and i guess different options will be used for different applications
And Circles.
https://joincircles.net/
It is going to get interesting now that exchanges are being shut down by governments around the world. I personally think the trustchain-based models are going to take over more and more as a result. The exchanges are unnecessary points of failure. And Bitcoin is unnecessarily centralized around the exchanges.
It is very exciting times we live in. I enjoy reading about all ideas related to mediation of trust.