I just read this today http://www.newsbtc.com/2015/06/01/blockchain-sent-8k-worth-bitcoin-to-wrong-address/
Another 8k of Bitcoins are (probably) lost forever, if no one has the private key of the wrong address.
I think it is much more then 5000.
they are at least 7k, we have a confirmation from the owner of his old wallet https://www.youtube.com/watch?v=0tMXLDVpPs8
however i changed my mind i don't really think that 3M, like many are emphasize strongly, are lost forever, while it's cool and all to reveal that you lost your money, perhaps in hope to become famous or something or to be more recognized
telling to everyone that you have retrieved your coins back in some way(you remembered your passphrase, you found an old back up ecc...) it's more unlikely to happen...