I'm sure this has probably been discussed, so please point me in the direction of those threads if it is true.

What happens if the value of a bitcoin reaches a level where it's easy for an entity to buy a large chunk of them and then send them into oblivion?  Could the system sustain a loss of 5 million coins?  At what percentage loss would the system be unusable?

Also, if we lose just 1/5th of a percent bitcoins per year (due to mistakes and what not) we will lose half the available coins in 210 years. (I hope my math is correct )