All this week, Marketplace Tech is looking at Bitcoin. The cryptocurrency's price has soared. Banks and governments are starting to pay attention and develop monetary policy when it comes to the form of digital cash. We plan to talk about everything from how to make it to who is holding it. But first, what the heck is Bitcoin? Plus, how Facebook can benefit from joining the S&P 500. And, Google stops letting Android users block apps from accessing non-essential data.