That's a neat find, I recon they have become more prevalent over the past decade or so with the access of the masses to GPS. I have never dug one, but I try to stay away from high traffic areas. I know there is at least one in the local state park. I have watched a family look for one last summer as I was detecting in the grassy area near the beach. To each there own I guess.
Cool little find. I still geocache from time to time, even have a few hidden myself. They are worldwide. There is one aboard the ISS and one on the bottom of an ocean somewhere. According to Geocaching.com, there are over 3 million geocachers. My grandkids love it. To them it's treasure hunting.