Amazon recently made some changes to the ways customers can share their Amazon Prime membership. It used to be that you could share the subscription's free two-day shipping with four other people. But as of last week, Amazon put a stop to that.

Its new policy says that Prime customers can add just one other adult to an account — and you've got to be cool with that person having access to your credit or debit card for purchases. They can add their own cards, of course, but payment methods will be visible to both people sharing a Prime account. This is a mandatory requirement if you want to share Prime moving forward.

In order to share content, Prime benefits, and Amazon Mom benefits, both adult account holders need to authorize each other to use credit and debit cards associated with their Amazon accounts for purchases on Amazon. This will not affect either of their current payment settings, but each adult will be able to copy the credit and debit cards of the other account to his or her Amazon account and use them for purchases with Amazon.

With the change, Amazon is clearly positioning Prime sharing as a household convenience meant for two partners or a family. (The company always "required" everyone to have the same shipping address, but rarely enforced this policy.) Note that both people in an Amazon Household get access to Prime Instant Video and the Kindle Owners' Lending Library — but that was already the case before.

It's still convenient if you've got kids, though; four children can be added in, and they don't even need dedicated Amazon accounts to watch Prime Instant Video. But splitting the annual $99 fee between four friends just got way less practical. Thankfully it doesn't seem to be retroactive, so if you leave your account settings unchanged, you shouldn't lose whatever sharing setup you've got in place now.