I've never quite understood the natural objection to lost coins that some people seem to have. Many other perceived problems with Bitcoin are explained but this one is usually taken as axiomatic.
Is it the lost granularity that concerns people? Is it a fear that people will hoard bitcoins? (Economic flamewar aside, I don't see why hoarders would be less likely to lose coins than everyone else).
Perhaps it's just because existing currencies are not so fragile. I don't see a gold forum parallel to bitcointalk.org with topics like "Help! I accidentally launched 3.8 tonnes of gold into deep space."
The problem as I understand it is that there is a finite number of Bitcoins that will be mined, 21 Million. After that any coins that are hoarded and forgot about or destroyed by damaged media, are out of circulation, forever. This will lead to the number of BTC shinking over time.