By requiring ripple accounts to have at least 200 XRP for it to be functioning, OpenCoin Inc (who I feel is hardly open) is creating an artificial demand for the premined XRP (Ripples). This is akin to tax required in the nation's fiat currency to artificially create use cases for that currency.
Good point. XRP is form of chartal money. It's like a coupon.
BTC, on the other hand, is entirely a boot strap asset. The good thing about XRP's chartal nature is that as long as Ripple is being used, there will always be some sort of core non-monetary demand to anchor XRP's price when it falls. BTC doesn't have a non-monetary component so it lacks an anchor to the downside. No reason it can't hit 0.