I came across a cache that supposed to have a cache camera in it for pics to be posted on the cache site. I couldn't find the camera, but I did find this post from a newbie (4th cache found):
"We found it! Nice park, great place to throw golf discs. We took a camera, and Bud TB. We left a blue lunch box, Mike Wyzowski, and a hand crafted Paduak pyramid with magical properties. Be extremely careful how you relate to it! Had a great time, TFTC."
(emphasis added)
I think this person was ignorant rather than malicious, but it was the worst trade I have seen.