Amazon released a video today promoting its Amazon Go stores and their “Just walk out” technology. Users check in with their apps at the door and then fill their shopping bags and leave. For now there is just one store and it’s in Seattle and only open to Amazon employees, but this location is expected to be an original that will spawn many copies.

“Just walk out” may sound great but is not without controversy. Jason Gardner, CEO of the payments platform Marqeta, spoke to Bank Innovation last year about the need for a “payment event” in shopping, which the Go stores currently do not seem to offer — though a digital receipt is provided after one leaves the store. “Lack of an event can lead to uncertainty, and loss of trust,” Gardner said. Ron Shevlin research director at Cornerstone Advisors, has made similar points. It appears those assertions will soon be put to the test.