[emillerm]

The issue with using this for loyalty cards is that in my experience, many stores have scanners than can't scan a glossy screen very well.

Also, the skeuomorphic design is nice but you could easily fit more cards on the screen by using a simpler list view.

[jvdh]

It's not only the glossiness, it's also about the original size. Barcodes work because they are at a fixed size, and a picture on screen can seldom reproduce the exact same size.

This is also why QR Codes have reference points (those three corner blocks or the big centre block)