Comment by whatsupdog

What Ethereum did after DAO was way more sinister. At least with the Bitcoin "roll-back" there were no transactions reversed. The miners just got together and started mining from a previous point in the Blockchain, and eventually the new chain had more work done and was validly accepted by even outdated nodes. Ethereum just went ahead and added this to their protocol: "ummm this transaction stands reversed, you don't need to verify signature for this particular transaction". This blot will stay in the protocol for ever.