Someone will try. They will fail. (a soft authority, "The Bitcoin Foundation" was an early attempt. It failed)
Bitcoin foundation was an attempt to provide advocacy to the cryptocurrency. Something that is still needed today.
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I think Slark has the right term here. Advocacy not authority. No entity has any authority over BTC. No one can change the supply, distribution, usage rights. These things are coded into the protocol and could only change with overwhelming community consensus.
No, you've both got it wrong. If Bitcoin is really better than using fiat currency or payment networks, then it doesn't need any promotion besides word-of-mouth. And everyone knows that word-of-mouth is the most trustworthy form of advocacy; you don't hear word-of-mouth recommendations from people that aren't your friends.