Quite possibly the most useful advance in the world of commerce in recent years is the cash card:  Essentially, it's a refillable gift card for a store that usually sells frequently-purchased, small-ticket items.  The Starbucks Card is a good example.  And I just came across the Subway Cash Card.  There are at least 5 reasons why these cards are an incredibly great idea: 

1. They're easier to carry than cash.
2. They're faster than paying with a credit card (there's no receipt-signing involved).
3. I can still earn credit card points when I purchase and refill the card.
4. They're unlikely to cause major damage if stolen (stealer can't access bank records or charge anything).  Plus, they usually don't carry balances over $20-30.  And Subway's card has a few theft protection measures on their website.
5. The stores are getting guaranteed repeat customers.

In my research for this post, I found out that Dunkin Donuts, McDonald's, and many other places have cash cards.  I guess any store that sells gift cards would function in the same way.  But places like Home Depot and Target are slightly different:  They treat the card like a credit card, so there's receipt-signing and other time-wasting processes.  My advice for stores that want to make the cash card system work is to make it as fast as possible.  Just swipe and go.  Otherwise, there's no benefit to using it instead of cash or normal credit cards.