I have thought about this as well.  Has there been any discussion of setting an "official" conversation rate for BTC?  That seems like the best policy at first glance to me.  Then people can use BTC without any fear that their value with go up or down like 1 hour later, and it won't destroy the fiat system.  But I bet many BTC ppl WANT to destroy the fiat system, so that probably won't work.