I think both the US and Australia (and probably other countries), should just do away with the $50 and $100 bills. It becomes a lot more inconvenient if you have to carry around 5 times as many briefcases of cash for illegal transactions.
You do realize that there are large legal transactions that should be allowed to be made without privacy violations, don't you?
... or wheelbarrows
If you're going to do illegal stuff, I don't think carrying around a lot cash if going to weigh too heavily on your mind. You're either going to carry it in a car or have a person carry it for you.