The fed wants to own everything. They are currently purchasing debt to the tune of hundreds of millions of dollars worth every month. Because of this, the interest rates are staying low and the leverage bubble keeps expanding. Because debt has ballooned, the fed is currently stuck in a nasty feedback loop and they can't get out. If they stop buying debt, rates go up, if rates go up, they can't afford interest payments on the debt. What this means is since they can no longer control inflation or the bubble, the crash will be unprecedented. It will take our entire monetary system down.