Seriously, I read a couple of web sites on this stuff, and the thing I find most interesting about it is that the crop circles show up in a bunch of different places all over the world, and the techniques seem similar. I don't believe the UFO stuff, but it's got to be a pretty tight group to keep it a secret this long. The Bigfoot in a freezer guys only lasted a week.
Hell, man, it takes little more than a well-organized team of lawn mowers carrying GPS receivers with waypoints programmed in. Same method as corn mazes.
As for "world-wide," we've got a fine example of how people from all over get together and plan and discuss things right here at FR. And gaming communities are far more organized than we are. It's easy to predict that there's a "crop circle" community out there somewhere.