I wondered how much bitcoins are already lost (I know there is no posibillyty to determine an accurate amount) ?
BTC can for example be lost if someone forgets the password of his wallet/ looses wallet.dat
Is there any estimated amount ?
There are obviously Satoshi's addresses (and private keys which he claims he won't use).
Beyond that, I'd say it'd probably at least 10000 bitcoins that have been lost due to forgotton passwords (based on the history of this part of the forum).
Also some early miners may have lost/deleted private keys as soon as they ined blocks.
Any coin that hasn't been moved since about 2012 is probably one powered by a private key the user at that time had no access to.