The more experience we have, the less we trust each other !
That's why maybe we need proofs and evidence. That's why maybe we look for reasons to be sure of what we see, think and suppose !
Proof of work :
The proof of work has existed for centuries and maybe for million years. I think since the humanity appeared they started to build relationships. So, when a new member in a family or a group pops up, he/she had to work to prove the usefulness to others. The work can be mental and that's by acting the proper way to be accepted, or it can be physical. So, the last one gets monetized during the time and we just get used to seeing people rewarded for their work that way. That's how the creator(s) of bitcoin decided to reward those who mine it. And we have the same on our blockchain where some are rewarded by liquid tokens or in form of upvotes.
Proof of concept :
We usually hear it only in ethereum without thinking that such concept could already have existed. How many times we saw a worker getting appreciated by doing something special for the company? That's maybe coming from the motivation to improve. When a worker sees that his earning isn't growing and wants to make more money, he/she decides to be more useful to the company and starts to think about cool ideas to improve the work and in the end gets rewarded for that by career growth. That's how the proof of concept existed even before ethereum. The same we are doing here when someone creates a useful application or valuable community or does an exceptional thing.
Proof of brain :
That's a combination of many proofs. Even in real life we may see that when inventors get rewarded for what they create, think or discover. Maybe that wasn't given a name, but it's a proof of brain. When smart people are appreciated by the public not only with monetary rewards, but also with respect and encouragement and they may be very wealthy people because of that. The same about those who are supporting the proof of brain on this blockchain by sharing their practical ideas. That's why I think the proofofbrain tribe has a big future and people here will thrive.
Proof of activity :
Of course the most active people get always rewarded during the history. Because they may learn more by their activity and in the end bring more value. Talking about social media, those who share more content in form of posts or comments are usually rewarded by becoming popular which may bring them a lot of
benefits. The same about the activity on the blockchain: the more people will notice you, the more rewards you may get. That's why we should be active commenting others and at the same time active sharing our ideas outside in forums and other crypto communities.
Proof of promotion :
When growing in a community or a company comes with good results. The member starts to see a big future for him/her and others. And the more people there are happy about that, the bigger chance that a big promotional company will start. The owners will not even have in this case to care about the marketing. Such system may promote itself and that's usually the most successful way to turn that into a brand. It could be even an international brand getting known by everyone. If we apply that on the blockchain, we will not need any promotion and people will know us by a word of mouth.
Proof of value :
The best proof maybe should be the proof of value. Because when people realize that someone is already bringing a lot of value, they will reward him/her. That way if a company or a community brings value to the world, it will be well known, successful and of course always rewarded for that. Such people don't care that much about the return. They just keep bringing value because they enjoy doing it.
I don't know if other proofs still exist, but it seems that I already mentioned the most valuable ones.