I've gotten pretty good reactions to "Bitcoin is Cash at a Distance"
which I wrote into this article on a friend's marketing blog. http://www.v3im.com/2012/07/interested-in-mobile-payments-bitcoin-is-cash-at-a-distance/#axzz228ZEPkeN
I think it's important to emphasize how like cash bitcoin really is. Like cash it's immediate and relatively anonymous (yes, yes, I know it's not perfectly anonymous), it doesn't expose the payer or payee to identity theft, relieves the payee of payer identity fraud, PCI costs, chargebacks, floats, batching delays, and bounced checks. The big difference between bitcoin and cash is that bitcoin can be sent over the internet directly, cash can't.
Somebody on this forum (wish I could remember who) emphasized the idea of currency authentication, as opposed to payer authentication. In other words, like cash, you the payee just have to make sure the bitcoin sent to you is good (ie, not counterfeit/double-spent), you don't care about who is giving it to you because you aren't being authorized to take money from their account later on. They actually just gave it to you just as though they put cash in your hand. I love that about bitcoin.
I sometimes describe the difference between bitcoin and other payment methods as "giving money not taking it". Checks and credit cards are ways of authorizing someone to withdraw (take) your money via a 3rd party. Bitcoin is based on depositing (giving) money directly to the payee.