user57606: I understand that proof-of-work plus a block chain is one way of creating a trustworthy public ledger of transactions.  But holy hell, the cost to society in terms of energy consumption is VERY high per transaction.  I participate in conversations online all the time where I implicitly trust that I am seeing the full discussion and that everyone can see my input.  Usenet, for example, does this in a decentralized way.  Couldn't we just post our transactions to usenet save some resources?

user63872: 
I participate in conversations online all the time where I implicitly trust that I am seeing the full discussion

Proof-of-work is one part of what allows bitcoin to be trustless, which is a very important property for any decentralized system of value. If transactions were just posted to a forum, then what is to stop a forum admin from editing, censoring, or deleting transactions? 
Creating a trustless financial network is not a trivial task, the large amount of energy being spent to secure the network is a testament to the value users see in maintaining and participating in the network. 

57606: <p>I understand that proof-of-work plus a block chain is one way of creating a trustworthy public ledger of transactions.  But holy hell, <a href="https://news.bitcoin.com/analysts-debate-power-consumed-per-bitcoin-transaction/" rel="nofollow noreferrer">the cost to society in terms of energy consumption is VERY high per transaction</a>.  I participate in conversations online all the time where I implicitly trust that I am seeing the full discussion and that everyone can see my input.  Usenet, for example, does this in a decentralized way.  Couldn't we just post our transactions to usenet save some resources?</p>
 63872: <blockquote>
  <p>I participate in conversations online all the time where I implicitly <strong>trust</strong> that I am seeing the full discussion</p>
</blockquote>

<p>Proof-of-work is one part of what allows bitcoin to be trustless, which is a very important property for any decentralized system of value. If transactions were just posted to a forum, then what is to stop a forum admin from editing, censoring, or deleting transactions? </p>

<p>Creating a trustless financial network is not a trivial task, the large amount of energy being spent to secure the network is a testament to the value users see in maintaining and participating in the network. </p>
