I've been in a few stores where they were clearly placing stickers on top of the bar codes to make it more difficult to price check... fortunately, most big ticket household items like TVs have unique product numbers that are relatively easy to search for, but I could see this discouraging a few shoppers.

For things like TVs, Best Buy et al tend to be price competitive. It's add-on things like the HDMI cables and extended warranties where they screw customers with hugely inflated margins.