If we get deflation, as many people are predicting, then you can get several percent "interest" just by holding your money in cash. That's built into the interest rate expectations for a lot of securities right now. You wouldn't see these near-zero interest rates unless people were expecting the dollar itself to become more valuable in the near future.

The Fed, with all of the T-bills out there, will never allow deflation. It's not in the government's interests.