Every lost coin is a donation to everyone else and all that
not realy.
You lose bitcoin but your wallet is still in the network. and it will never dissapear.
So your money wont be used by someone else never.
its gone forever and wasted.
He means that as the 'lost' bitcoins will never be used, everybody else's bitcoin gain slightly more value due to less useable bitcoin being in the bitcoin economy.
(I think deflation would be the term for this?, I think there's a better word...)
It's like the opposite of what happens to the value of your USD when the US Treasury prints billions of dollars and gives it to big banks.
Anyway bitcoin network has a lot of those and this is like normal that things like that will happen :-)
? 
