I used to work in Primark and we had loads of shoplifters. There was one who constantly came in and took whole rails of clothing, and was never caught. Why would you need a whole rail of identical jumpers in lots of different sizes?! If you were doing it for resale surely you'd steal from somewhere where the clothes were worth more than £5 each.
The security guards in Primark (the one I worked in anyway) are shoot, they spent all their time taking the piss out of me for looking like Kelly Osbourne (I don't) and no time investigating the shoplifter that a customer saw once and reported to me.
In fact, another useless security guard story, three security guards gave me a bollocking for pushing my bike through a shopping centre the other day. The shopping centre is a thoroughfare, I checked before I did it for signs on the doors (there was one with a bike with a red circle round it, which I assumed meant no cycling but you can push your bike, as that's what it means according to the Highway Code, and there was another of a skateboard with a red circle around it, which I assumed meant that you can't skate but can carry your skateboard). Apparently my crime necessitated three twatty security guards marching up to me and being rude. They implied that something horrible will befall me next time I do it, so I'm going to take my folder in and see what they make of that.