[mrb]

You are incorrect. When the "price fell to zero" in June 2011, it was the result of bogus trades from a hacker: http://blog.zorinaq.com/?e=55 No one had enough bitcoins to crash the price that low for real.

As of today there are so many bids on MtGox alone that selling 100k bitcoins is barely sufficient to crash the price to the low $30s. Anybody owning that much is obviously long on bitcoin. It will take a lot more than a "few large holders" to crash the price to $30 or below. It would take a massive market panic.