Non-working security tags
Bought three (rather pricey) shirts from a large retailer at the mall. A few days later at home pulled one out of the bag - and found that the anti-theft device was still attached. Checked the other shirts, and found that only one had the security tag removed. So I walked out the door with three items nominally worth $285 (purchased) - and the two security tags did nothing.
Now I do not want to burn an hour driving back to the store, just to get the tags removed. I have successfully bashed this sort of tag to bits before - a bit of a pain - when the store clerk forgot to remove them. Checked to see if anyone had a better approach, and only came up with - Removing anti-theft devices still attached to purchased clothing and Removing security tags - nothing fancier than pliers and bashing with a hammer.
Looking for more information, came across an outfit selling fake security. The "fake" tags are much cheaper ($0.10 each) than the real tags. I have walked out of the store before with items where the security tags were still attached (when the clerk forgot to remove the device). Never had any sort of alarm go off. Apparently the use of "fake" security tags is pretty common.
The search turned up a fair number of court transcripts where the presence of the security tags was used as evidence. My guess is that fake tags are mostly just meant to identify shoplifted items when a shoplifter is caught by store security.