Had that in LCY where I printed my own BA boarding pass. First I wondered how the devil you can make sure that people do not fake a boarding pass with Photoshop etc. but then saw that the pass contains a very complicated pattern encoding your information like Flight number, day of departure etc.
It is then scanned before you enter security control and the scanner validates that you are actually on a flight that leaves today etc.

A good development IMHO.

Cheers
Christian