Anonymity - most people don't need or want it, and those who do need real anonymity, not traceable pseudo-anonymity. 51% attack - consider other uses like a sh

Anonymity - most people don't need or want it, and those who do need real anonymity, not traceable pseudo-anonymity. 51% attack - consider other uses like a shared ledger between 5 big banks, all of a sudden you just need 3 colluding and your blockchain is broken. Or bitcoin, most of the miners are in China, the state intervenes one day and secretly requires collusion. POW - 7 transactions a second, minutes to confirm and massive costs for those keeping full copies of the chain are big stumbling blocks to any blockchain based on POW as in the example or bitcoin. I think it has some fascinating ideas around shared trust, but Blockchains based on POW are fundamentally unsuited to the sort of large networks of transactions they are being proposed for and centralised solutions involving signing or hashing have the same advantages but solve all these problems and others like trust.