From what I know about BTC, it's engineered so that the currency is constantly operating and "peak mining" - if mining begins to fall off, within a certain number of cycles mining will become easier, thus making mining more profitable again.
The point of that is to keep the rate of block solutions relatively constant, regardless of how many people are mining. After the last big price crash, it was instantly extremely unprofitable to do any mining, and the number of miners crashed overnight. eBay was flooded with 3d video cards. So the difficulty came down again until blocks were being solved regularly, but no one was making any money unless they weren't seeing their electric bill (or had really low local rates).
