For a long while, Amazon would let you share some of your Prime perks with four other people of any age -- handy if your roommates need to get an order in a hurry. However, it looks like the internet shopping pioneer is clamping down. A quiet rule change on July 31st has limited Prime sharing to one other adult as part of an "Amazon Household." Moreover, that other grown-up has to use the original member's credit card (update: not really true, see below). That's fine if you're sharing it with a significant other, but lousy for anyone else.
The good news? The changes don't appear to be retroactive, so you should keep your sharing benefits as long as you don't shake things up. With that said, it's clear that Amazon wants to wring out as many extra Prime subscriptions as possible. That's not entirely surprising -- Amazon is still loading Prime with an ever-greater number of high-speed delivery and streaming media services, and the only real way to keep up the revenue per service is to get more subscribers.
Update: You can use multiple cards in an Amazon Household, but you have to authorize the uses of each other's cards. It's possible to copy cards from one account to another, too.
[Image credit: AP Photo/Ross D. Franklin]