I've criticized the USPS a few times recently, and frankly, for good reason. They just aren't that good at what they do.* But just to show you I'm not a terrible guy, I'm going to try and pitch in and make mail delivery both more pleasant for users, and more profitable for the USPS. Here's my idea, which may turn out to have a fatal flaw I haven't noticed, but unlike the mail carriers in any Post Office I've ever been to, at least I'm trying.
(* I should be mad at them, in fact. I just got my baptismal certificate mailed to me, and it was nearly ripped in half. Don't worry though, all the Container Store fliers in today's mail were in pristine condition.)
The plan is that the USPS set up a way to buy stamps online, sort of like Stamps.com, but forget about actually printing any stamps out. What customers do is log onto their account, and indicate that they're ready to mail a letter, and input the zip code of the recipient. The postal service then gives them a very large random number, and deducts the price of a first class stamp from their account. The customer writes this number on the envelop in the place of a stamp. The postal service scans the envelop upon receipt, and reads the number. If the number on the envelop corresponds to a number they have sold, and the zip code on the envelop matches the zip code associated with the number when it was activated, the letter gets delivered. If not, return to sender.
By selling only a small fraction of the potential numbers in the range being used, and selecting them randomly, you prevent people from guessing a number and taking their chances on not paying. By associating it with a zip code, you prevent people from stealing the number on someone else's outgoing mail to use for themselves (unless the thief also happen to want to send a letter to someone in the same zipcode, in which case you could associate the mail number with the street address rather than just the zip code).
Furthermore, because every letter mailed in this way has a unique identifier, this can function as a built-in tracking number.
The big benefit over Stamps.com is that you don't need a printer. All you need for my scheme is a web-enabled device and a pen. Customers never have to worry about running out of stamps, or loosing them. The postal service doesn't need to worry about printing and distributing real stamps. Boom. Victory.
(This seems like such an obviously good idea to me that I'm getting that tingly feeling I get when I've overlooked something obvious. Did I leave something out? Is someone already doing this?)