After all, Black Arrow belongs is a hardware supplier who actually fabricated and shipped miners. Only a few providers have this reputation at the moment.     

Actually, why is the BTC/$ value on BTC-e so far below the BTC/$ value on MtGox?

The difference is about 200 $ at the moment.     

There is only a very little chance that all bitcois dwindle away with time. With the value of bitcoin constantly increasing people are more and more careful in keeping their bitcoins in a save place. Of course, many bitcoins will be lost in the future - maybe there are only 100k left in 2100. But this would also be a time in which your descendants receive wages and pensions in femtoBTC.       

The strong increase in value of the BTC is actually supported by massive investments especially in china. Due to the lack of opportunities as they are common in the western hemisphere a load of Chinese people see BTC as a very attractive capital investment.