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From the beginning, the main goal of Amazon Prime, the membership program that includes benefits such as free two-day shipping on all orders, was to get consumers into the habit of buying regularly at Amazon—to change “people’s mentality so they wouldn’t shop anywhere else,” in the words of one former Amazon staffer. Because the Internet giant has been especially eager to get moms into the habit of shopping at Amazon, for years it has made them offers many caregivers could not refuse, including a year’s free Amazon Prime membership and hefty discounts on diapers and other essentials. Starting January 24, though, Amazon Moms won’t have it quite so good.

Members of Amazon Moms recently received an e-mail notifying them that the program was changing. It reads:

* Starting on January 24, 2012, the maximum discount available on diapers and wipes subscriptions will be 20%. This includes a 5% Subscribe & Save discount plus an additional 15% exclusively for Amazon Mom members who are earning free shipping benefits or have an active Amazon Prime membership. * Customers who join Amazon Mom in 2012 will get three months of FREE Two-Day Shipping benefits. However, as a founding member of the Amazon Mom program, you were eligible to earn up to one year total of free shipping benefits.

(MORE: Amazon Prime Loses $11 Annually Per Member — And It’s a Huge Success)

Translation: The benefits Amazon Mom members have grown accustomed to won’t be as good.

Before the changes, Amazon members were eligible for discounts of as much as 30% off diapers, and two-day shipping was free for a full year. New members will only get free two-day shipping for the first three months of Amazon Mom membership.

Speaking of which, it’s unclear if it’s even possible to join Amazon Mom at the moment. Right now, there’s a message at the signup page reading:

Looking to join Amazon Mom?

You’re in the right place. But at this time, we’re not accepting new members to our program. If you’d like to be notified when Amazon Mom memberships reopen, please join our waitlist.

Presumably, membership will reopen as of January 24, when the program rules change. It seems as if Amazon cut off membership signups in anticipation of a mad rush to join while the more generous benefits are still in effect.

(MORE: How Amazon Gets You to Stop Shopping Anywhere Else)

In any event, Amazon Mom is changing, and plenty of Amazon Moms aren’t happy about it. A thread in the Amazon Forums is full of parents griping that the program is a “racket” designed to lure them into paying $79 a year while shopping almost exclusively with Amazon. One mom wrote:

They advertised all there[sic] great benefits and so many moms “took the bait” and then they just snatch out from under us.

Following in the footsteps of protests against Verizon Wireless and unpopular debit card fees, a petition at Change.org has been created requesting that the original Amazon Mom program be restored.

The petition is addressed to Amazon CEO and founder Jeff Bezos, who just so happens to have been named MarketWatch’s CEO of the Year 2011.

In the past, it’s been reported that Amazon Prime loses $11 annually per member due to benefits such as free two-day shipping and streaming of digital content, along with extended complimentary benefits for moms and Amazon Student members—who get free Amazon Prime shipping services (but not all of the usual Prime benefits) free of charge for the first six months of membership. That “loss,” however, is usually more than made up for by the profits Amazon earns on members’ purchases.

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Nonetheless, it appears as if Amazon feels that by now, Prime has proved itself valuable enough so that it can trim back discounts at the same time it’ll start collecting annual fees sooner from members. Not long ago, offers used to surface granting one full year of Prime shipping benefits for students, but no such promotions have popped up recently. The hope is that Amazon Mom and Amazon Student members are hooked on the service to the extent that 1) they won’t drop membership, even if benefits become less generous; and 2) they’ll one day become full-fledged lifelong Prime members paying $79 annually.

Brad Tuttle is a reporter at TIME. Find him on Twitter at @bradrtuttle. You can also continue the discussion on TIME’s Facebook page and on Twitter at @TIME.