Someone could own that much of the dollar market, but yes this have more to do with there being much more speculators than users of bitcoin who control the majority of the fund. If everyone on the planet only trade fiat currency rather than using it as a currency, you're going to get a lot of fluctuations too.
That's very hard, because the central bank can hold against it. They generally don't do that if a fiat currency loses against another fiat currency (sometimes a bit, but that's more for psychological reasons), they do it to hold the currency on a small price rise rate (which is seen as useful by most economists). Also as I wrote above: Most people don't have that much money, even if they have a lot of wealth. But with Bitcoin there is no such stabilizing entity, it's all on the market. And markets tend to fluctuate a lot, even with high volumes. And from time to time there is a crash. That's natural. The question is: Is this really something we want for a currency?
Most people here seem to have an "everything will be fine in the long run" attitude. While this is certainly good to get Bitcoin started, I still see the problem, that Bitcoin is to much defined es a commodity instead of a currency. Its design is to mimik some properties of gold in this regard. But while gold has the big advantage to work very good in low-tech situations, it doesn't work that good in a world with world-wide stock exchanges and global trade and competition (that's why it got abandoned as a base for most currencies).
Gold is also still a nice way to store a certain part of personal wealth, and in the case of global economic and technological collapse it may get back it's role as currency. But that's because of it's physical properties - properties, Bitcoin don't have. If "the system" breaks down, Bitcoin will be useless because it depends on todays high-tech infrastructure which probably won't survive a real collaps.
So what I did was making the order processing partially automatic; the customer select Bitcoin during checkout in the online shop and gets information how to proceed in the order confirmation email automatically. When we receive an order I browse through the recent currency trade stats/graphs for the past days and reply with an offer via email which is time limited depending on how big the BTC currency fluctuations are against US Dollar.
But this only works because we have the Dollar as a relatively stable benchmark. Without such a standard it would be much more difficult to really judge how to fix your prices. You would always have to match it against your purchase and restocking prices. While this would be possible, it opens up lots of potential problems which are hard to handle. Because of this, bigger companies often use futures and the like to protect themself against such currency risks (which do exists in fiat currencies, even if to a much smaller amount an primary in international trades between different currencies). Now imagine, everybody has do do something like this because of much higher currency volatility.