In case you think that's theoretical, a bug with integer overflow let an attacker creating 184 billion bitcoins out of thin air. To fix this, a new implementati

In case you think that's theoretical, a bug with integer overflow let an attacker creating 184 billion bitcoins out of thin air. To fix this, a new implementation was pushed out, which ended orphaning more than 8 hours of transactions. In other words, even after 8 hours you can't be certain that Bitcoin transactions are durable. https://en.bitcoin.it/wiki/CVE-2010-5139 https://en.bitcoin.it/wiki/CVE-2010-5139 Another interesting case is when bitcoind 0.8 changed the underlying database from BerkeleyDB to LevelDB. Due to different database lock limits, bitcoind 0.7 couldn't process a block that bitcoind 0.8 could. For 6 hours, there was a fork where old clients were using a totally different blockchain than new clients, because of this single block they couldn't handle. This is what patio11 means, that you have to be bug-for-bug compatible with the reference implementation. http://bitcoinmagazine.com/3668/bitcoin-network-shaken-by-blockchain-fork/ http://bitcoinmagazine.com/3668/bitcoin-network-shaken-by-bl...