Ask HN: QR code loyalty programs prone to abuse?

If you've been around the bay area, I'm sure you've seen the litany of QR code based loyalty programs where after you purchase something, you download an app and scan a QR code that the employee pulls out from underneath the counter. Once the scan is completed, it virtually "stamps" your card so that you can get something for free when you accrue enough stamps.

My question is doesn't this make it completely prone to abuse if I simply took a photo of the QR-code instead of scanning it? Even if the employee watched me open the app, I can simply use a screen capture shortcut on the iPhone to accomplish capturing this QR code that I can scan anytime I want in the future.

I haven't tried it yet and you may say it's not worth much but given how many businesses are moving to this, it would seem some folks would abuse it for free drinks and food daily.

Wouldn't a better solution be to have a unique QR code tied to YOUR app and then have their scanner read your screen vs. the other way around?