I guess it is funny if you see it once in one location and make mention of it. This scale of prank feels more like a DoS attack. Honestly I hope the organizer has to pay the fine for how much time it takes the people who need to fix these errors.

Knyte wrote:

He attached them with magnetic tape. How long does would it take someone to remove them? 0.5 seconds? He also didn't remove any real tags, they just added the new ones in.

For the next few weeks the Costco employees have to walk around double checking for these things. Some customers will undoubtedly be offended or confused. Also, when they do catch someone fucking around they have to deal with them. That takes time and effort. All in all, it isn't that funny and it causes a loss of productivity for Costco.