I don't particularly care for the receipt checks. However, I do understand why, and in Costco's case, I accepted this when I bought my memership.

Several years ago, I went to Fry's Electronics to buy components to build a computer. One of the items in the pile did not get scanned. I didn't notice the item not on the list, but was initially happy to see the lower than expected total. On exit, the "inspector" found the unscanned item. I went back and paid for it seperately. In their case, that 30 seconds of time saved them several hundred dollars in lost merchandise. Unfortunately in today's society, this type of loss prevention is also necessary to cut back on theft. I guess you can vote with your wallet and shop elsewhere, but in my case, I'd rather not have the higher prices to pay in the store to offset those losses.