I should add that it doesn't really matter if Bitcoin is "lost" because all that does is increase the value of all the remaining coins that all the other people hold. It's only good for them.

It's not like we're ever going to run out of units because each Bitcoin is evenly divisible down to 8 decimal places. So we can access units that are as small as we want, and if we had to, we could subdivide them further in the future if/when necessary.