Uber is the swanky cab-alternative car service that’s been spreading like wildfire in some major US cities. But to throw gas on that wildfire the Uber team decided to do a cute on-demand ice cream delivery promo that tied into their app. Unfortunately the promotion encountered that all-too-common pitfall of “sounds awesome on paper but fails abysmally in the real world.”

Uber apparently underestimated the popularity of free ice cream and couldn’t meet demand. Plus, users weren’t too happy with the promotion’s usability and unhelpful error messages. The experience of the Fast Company staff seems to be shared by quite a few users (though to be fair, the promo worked splendidly for some people).

It’s late Friday morning, and a cheerful new ice cream button appears in the Uber app, alongside icons for its regular black cars and SUVs. Can we get one that plays the classic ice cream truck jingle?

We holler for one of the six Uber ice cream wagons in town around midday. … A request button pops up that lets us pinpoint our delivery location.

The Uber app informs us no ice cream trucks are currently out on the road.

Nice try, Uber. We know you’re out there–we see people on Twitter munching away happily, with the pics to prove it.

So ice cream trucks are definitely out on the road. Just not on our road.

Wait, progress? A few more futile requests later, a new message pops up. At least now it’s telling us all the trucks are actually out making deliveries, but it’s been two hours and we still don’t have any ice cream.

People are getting increasingly antsy from the lack of a queue or system that lets us track our place in line. We all keep tapping our screens in search of an answer other than “Sorry.” …

And everyone who didn’t get their ice cream? They unleashed an #uberfail hashtag parfait with vitriol sprinkles.

But the lesson here is pretty clear: Uber should remember that at its core, it is a car service, not a chaotic ice cream free-for-all. When you peddle something as universally appealing as ice cream, it’s a given that you won’t possibly be able to satisfy everyone, even if you had dozens of trucks at the ready. Yes, Uber ended up spreading the word about its core business, but it was at the expense of the ill will it generated from a marketing ploy that made people feel like children on the wrong end of a cruel prank.

The Fast Company article has a ton of great supplemental images and tweets, so check it out >>>

Usually I’d put a note about the lesson we learned about preparing for real-life, in-the-wild situations here, but the Fast Company already did it for me with that last paragraph. Plan for in-the-wild scenarios people!