Hear, hear! mkj's article on anonymity is worth reading.
From my perspective, the most important thing cryptography offers us is not just the ability to have private conversations without eavesdroppers; it's the ability to change the balance of power from the centralized control and accumulation of information that computers bring back to a level where _you_ can control what happens to your personal data.
Do you _like_ starting transactions by giving some big company your Social Security Number which lets them, and everyone else, know everything you've ever done, where you live, how you vote, what you buy? We can move to a society where you can give the other party as much information as they need to do business with you, without having to give them everything else, or connect this transaction to all your others. Sometimes that means giving people more detail than you give them now, usually less. Cryptography becomes the technical glue to control how much you tell somebody on each transaction, anywhere from total anonymity to deep personal information, to let you have a driver's license that says "yes this person is a safe driver" without it becoming the key to your bank account of you lose your wallet, to have voter's registration that doesn't permit fraud but doesn't require universal identification. Some good technical references are the set of papers that David Chaum published about blind signatures and anonymous credentials. Bill