Probably every third time I walk into or out of a shop, I set one of these fecking things off. Sometimes it goes off on the way in but not on the way out 
I was in Morrisons today and every second customer activated the alarm.
Last week, I absent mindedly walked out of Boots without paying for some make up and the alarm didn't go off but it did when I went back in to pay for said make up. I don't see the point of the damn things as apparently loads of shoplifters know tricks to avoid setting them off.