> - Loses accepted transactions!!! (blockchain forks, orphan blocks, etc) From a distributed database perspective the Bitcoin blockchain is broken and loses data: like a decentralized MongoDB, but slower by several orders of magnitude.
When a block is orphaned or when there is a fork, transactions are not lost, they'll always be present in the main chain. Or said another way, all miners are trying to mine the unconfirmed transactions in their mempool. If one miner ends up finding the winning block, transactions they didn't include that were included in an orphaned block are going to be mined in the next block.
What you may be referencing, though, is not "lost transactions", but rather double spends? What I said above holds true assuming no one else is trying to spend the same outputs. However, if you wait 6 confirmations (the recommended amount before you should consider a transaction "accepted"), you won't see double spends, either.
When a block is orphaned or when there is a fork, transactions are not lost, they'll always be present in the main chain. Or said another way, all miners are trying to mine the unconfirmed transactions in their mempool. If one miner ends up finding the winning block, transactions they didn't include that were included in an orphaned block are going to be mined in the next block.
What you may be referencing, though, is not "lost transactions", but rather double spends? What I said above holds true assuming no one else is trying to spend the same outputs. However, if you wait 6 confirmations (the recommended amount before you should consider a transaction "accepted"), you won't see double spends, either.