The value of gold can also crash real hard too. I love to use the analogy of finding some ultra-pure veins of gold on some asteroid. If you could get a million ounces of gold @ $10 USD per ounce (in theory something which could happen), it would certainly send the gold markets crashing if those guys decided to dump it on the world markets all at once. The days of a major gold rush to somewhere still aren't over, but they are going to be found in more exotic places than we've seen in the past. If that happens, Bitcoin users are going to smile and those who are hoarding gold are going to look foolish. The only similar kind of event with Bitcoins is if somebody who is hoarding a large number of bitcoins decides to dump them onto the major currency exchanges for Bitcoins to push the value down. I think that would only be a temporary situation anyway. Somebody doing that is also shooting themselves in the foot, and self-interest is one that would encourage you to put a large hunk of Bitcoins into such a market much more slowly.
This actually happened to the spanish during the colonization of south america. They brought so much gold back to spain from the new world at such a low cost that it caused monetary inflation(they used gold as money then) It also disrupted their internal wealth calulations.
However, despite the disruption, it remained valuable.
If we find a gold asteroid today, it won't even disrupt society(gold is not money, we don't use it for value calculations). It will just drop the value calculation via the dollar. It will still be an excellent wealth reserve because people will still want it.