The Apple iPhone will soon be functional as a credit card processing device, according to this report on Finextra.
What this means is that your landscaper, the seller at the flea-market, and other small enterprises will be able to process your credit card using their iPhone as a mobile card authorization unit. There are monthly fees and such, but that's already standard in the credit card world.
This is a potentially huge greenfield market. I've been wondering why PayPal hasn't launched some capability like this, accessible using the browser function on smart phones.
A commenter on the Finextra story says that Treo has had this capability for some time. He recounted how a tour guide was easily able to upsell customers mid-tour because of the simple availability of card processing. It is well known that having-card users tend to spend more than cash users, and this has long been a selling point for merchant services.