Wouldn't lost bitcoin be one of the inherent faults with the bitcoin system? It seems inevitable that a huge percentage of bitcoin will eventually be locked/unusable as people continue to lose their wallets or passwords, etc. What happens when 25% or 50% of bitcoin is "lost"? Of course, maybe by then, we'll have already moved on to a "better" cryptocurrency.
It's great for the rest of us because less coins means more value for the ones that are accessible. Think of it this way, they cannot sell those coins cheap, so it keeps the price higher.