BitCoin will be made illegal, but cryptocash is here to stay
dbasch.posterous.com
dbasch.posterous.com
So you wouldn't strictly starve...
In order to become a force which could get attention, BitCoins would need to be used en masse for nefarious or questionable purposes (the definition of those being whatever politicians decide they are). Right now the volume is extremely low and quite frankly you're not going to conduct large scale illicit activities in that system easily. If it hits $50bn in volume however, then something might happen.
The value proposition of anonymity is highly valued there I suspect.
Prior to that occuring, I expect there would need to be a service that pornographers would 'buy' as enabling this as a valued currency.
So once we see the emergence of a referral system or advertising system in which you can 'pay' for ads with Bitcoins I don't doubt we'll see sites that accept Bitcoins as payment.
Despite those industries' efforts and help from various world governments, MP3 filesharing, still exists. Likewise, it seems possible that BitCoin exchanges will still happen despite it being illegal.
Is there a way to even shutdown BitCoin or would it turn into a pseudo-arms race like filesharing has become?
1. Create (discover) bitcoins using your own computer. This is slow and requires a lot of processing.
2. Provide a good or service in exchange for bitcoins.
3. Receive them as a gift.
That is all. I've ruled out theft, i.e. stealing someone's wallet from their computer.
That answers your first question. The second question, about how the supply evolves, is more complex. My understanding is cursory, but I'm pretty sure the bitcoin.org web site addresses it in depth.