Tampering with RFID Security

If you tamper with security systems, you will get burned sometime. I'm not allowed to enter this store for the next month, and i'm not allowed to touch any electronic equipment... So, i couldn't verify this on my own, but a good friend of mine took care of it :) A week ago, my university card (an rfid card for payment inside uni) stopped working inside my wallet. I found an aluminium foil stucked inside the wallet and whereever i put it...it stopped working...sooo...the aluminium isn't blocking anything. More likely is the thesis, that the foil reflects some waves and the anti-collision calculation will be messed up and the tag is invisible. Our theory was: if you put an aluminium foil near a tag, i won't be detected. The same should apply for those gates in clothing stores or bookstores, if they are working on a rfid basis. Because there is highly amount of data to be scanned, it is only checked at the exit. Therefore in a bookstore, you can just put an aluminium foil inside of the book, and walk out of the store...nothing will happen... We were shocked, coz it was that easy to steal something. Using RFID for such high risk security gates is just wrong...it is a wrong by design... so long