I imagine it will look roughly like the last time it crashed:

http://static.guim.co.uk/sys-images/Technology/Pix/pictures/...

90% of the value were lost in a few months. The market seem even frothier this time so I'd expect the eventual pop the be harsher as well.

US government declares it an illegal currency, and if you accept bitcoins at your business you will be investigated. Game over.

Some numbers are illegal, but that's because they have particular uses (Crypto etc). How in the world would the US be able to declare possession and exchange of data illegal?

Child pornography stored on a computer is data. The possession and exchange of child pornography is illegal.

They would have to define it to ban it. Bitcoin would just evolve to no longer fit the ban. There are already dozens of other cryptocurrencies brooding- just waiting for a scenario where Bitcoin is pushed out to make more room for them.

A ban on bitcoin will work about as well as a ban on piracy.

Not really, since the success of bitcoin still relies on conversion to another currency.

Additionally, the same applies to those other digital currencies as well.

If speculators decide they've had enough and start selling, then the bitcoin will return to a value based on its usefulness for transactions, instead of its attractiveness as an investment. How far it can go down depends on the size of consumer bitcoin demand vs investor bitcoin demand.

http://bitcoincharts.com/charts/mtgoxUSD#tgSzm1g10zm2g25zv

This is the value over a larger time. Sustainable?

A massive chain-split that erodes confidence in the perceived value of the currency.

Gold is a tangible substance. BTCs are just data and we all know how volatile that can be.

They just had a split. They resolved it in short order and the value skyrocketed after that.

It was a relatively minor split. I mean a split where nobody can tell what's what. That would pretty much end this experiment.

The 'cryptobarons' or some currency speculators who hold large quantities of BTC could dump them on the open market and crash the price.