I recall one time I was standing behind the would be thief and he didn't notice me. I watched as he took a CD in the oversized anti-theft case, hiked his shirt and started stuffing it down his pants. He turned around, saw me. His eyes went wide and the CD was whipped out of his pants instantly. He was obviously at least a little scared of getting caught and having repercussions. However, I was later told by a coworker that he was known to carry a knife and I was lucky I didn't get stabbed. Don't know if it is true or not.Obviously, this involves some element of risk...physically and legally depending on circumstances. And “reasonable” force may be used.
Another time a group of thieves came in and I simply stayed at a location where I could watch them. They tried to distract me by asking to show them where such and such item was, but I didn't fall for it. One of them then asked, "Where are the condoms at?" to which I responded, "As if you'd need them." which got his friends to laugh at him and then they decided to leave. He stayed behind, slowly walked up to me and said, "I need the condoms so I can (fill in the blank) your mom". I responded with, "If you want to (fill in the blank) my mom, I pity you". His face turned bright red and he said, "You know, you're a real dork." and stormed off.