Bitcoin had a bug that was required an organized chain reorg back when it was early as well, but it's not regarded as fatal to putting trust in the chain now (search for "bitcoin value overflow bug", was kinda interesting)
More recently, Parity, one of the main developers of one the Ethereum clients, had millions locked up due to mistake in their smart contract code. They complained loudly, tried to get another roll back, and finally gave up... The overwhelming concensus was that Ethereum is no longer alpha grade, there will be no take backs ever again.