-B-
In theory, yes. In reality, no.
While people can and have lost their private keys, there is no way for the rest of us to truly verify that. We can look at the block chain and look for coins that haven't moved in some time, but is that because the coins are lost, or are they in cold storage, or just in someone's wallet who hasn't had the need to move them? Without true verification that the private keys are lost, you can't just use someone else's word as basis for assuming the rest of the coins are worth more.
I think some time ago, BTC-e was assumed of being bribed to list a coin on its exchange. When news came out, BTC-e opted to destroy those coins in order to assure the community that they weren't being bribed - they destroyed those coins by sending them to an address which couldn't possibly have a private key.
Coins destroyed in that fashion can safely subtracted foe the total current and maximum numbers of coins in circulation, but that should be the only reason for doing so.