Real money typically gets created at a fast pace. As a nation expands, so does its currency. It's an over-simplification, but the currency can even expand faster than the nation's worth, leading to inflation.
Bitcoin doesn't really have this problem. Bitcoins are generated very slowly--increasingly so. Eventually, the generation process will cease altogether. The result is that bitcoins are much more valuable. The worth of bitcoins has already been realized, because bitcoins are being actively exchanged. It would be difficult for them to lose this value. More likely than a crash would be a slow decline in worth as people move on to other virtual currencies, like Litecoin.
There is one exception: when there are no more bitcoins to be mined--and just before that point, the market will be in a volatile state. My guess is that the value will fluctuate quite a bit leading up to the end, either spike or dip randomly at the end, and then increase over the following month or two, with an eventual decline as miners move to other currencies.
