I agree without this as a "feature" there could essentially be a bit-currency backed by the dollar, ie. the Bitdollar, for use in exactly the same secure, convenient, fast, cheap, online, and semi anonymous way as the Bitcoin, but exchangable for a dollar at your local bank and vice versa... and of course with value controlled by the value of the dollar
Yes the dollar could also be a possible way to back a Bitcoin-like currency. It would actually be easier to back with a dollar because instead of having to pay to store the gold backing the "goldcoins" you could earn interest storing the dollars that back your "bitdollars". I didn't want to use the dollar in my example of backing a Bitcoin clone-like currency because people would probably attack the dollar aspect instead of thinking about the concept of a Bitcoin clone being backed by something.