Today brings a high profile removal from the App Store, as the popular AppShopper app is now missing from the store. The removal, publisher Arnold Kim confirmed to us, has to do with a new rule that Apple added back in September which governs the promotion of apps not your own inside your apps.

Specifically, the rule reads this way:

2.25 Apps that display Apps other than your own for purchase or promotion in a manner similar to or confusing with the App Store will be rejected

A low volume of behind-the-scenes developer noise about the issue has been going on since the original discovery. We’ve heard that several were in talks with Apple about why their apps should be approved anyway and that there had been rejections delivered based on the rule.

Back when the rule was discovered, we noted that it could mean trouble for AppShopper. Though the app that exists primarily to highlight deals, track prices and create wish lists, it’s harder to differentiate it in terms of looks and basic functionality from the App Store than, say, Kim’s Toucharcade app. Toucharcade offers

 Apple removes popular AppShopper app from sale as it falls afoul of App Stores new app promotion clause

As I mentioned when the news broke, any app that offers an extensive list of apps will need to worry about this new rule. Specifically, you’re going to have prove to the App Store review team that your app offers more benefit than Apple’s own offerings.

I spoke to Ben Guild, developer of app discovery tool App Map, who noted that Apple’s intentions seemed fairly evident.

“I think it’s pretty clear that Apple wants to caution companies away from building these sorts of Apps. App discovery is a really interesting space with tons of room for innovation,” Guild said, “but perhaps it’s a space that Apple itself wishes to solely focus on.”

Guild and his team had begun submitting App Map well before the new rule. But they were eventually approved for “providing significant alternate functionality,” he told me. “Others in this space may not be so lucky, as Apple may already only be allowing Apps now on a case-by-case basis. This could turn into a roadblock, and rejections may serve as a cautionary tale to spread within the developer community.”

Despite AppShopper’s absence, there are still dozens of other apps that provide very similar functionality. Perhaps it was a high profile target.

With the removal of AppShopper, it’s looking like Apple is very serious about how this rule is interpreted. So, if you’re a developer that offers extensive functionality that makes it appear and work very much like the App Store, I’d start worrying.