The real world economy is highly inter-connected. The only way for a virtual economy to survive is to inter-connect with the real world.
Brilliantly stated. The idea that Bitcoin must operate in a self-contained, self-sufficient ecosystem is foolish. As it grows in usage, we should expect to see greater exchange into and out of bitcoins for other goods, services, and monies. There is no reason to fear "cashing out" into any other currency - it harms Bitcoin's utility not at all.