PSUSA: IMO some of them are much too complicated for people to have done in one night, and especially not leaving a trace.
Below, Jaime Maussan (commentator from Mexico) shows a bit more than just some pictures but on the ground and sky views of the phenomena. It is an excellent series if you are interested in this detail. It is a little rough for those lacking Spanish but it actually is the best documentary I have seen for last year.
I[t] is about 60 minutes of your time. Crop circles are fantastick.
I bet if we could get pictures of this graffiti to whatever alien taxpayers sent these guys to explore strange new worlds to show them how their money is being wasted, these things would disappear for good. ;-)