Sure it does. See some of the other replies in this thread.
And whether a stalk is "bent" or "broken" is highly subjective, unless it's completely snapped into two, which is most unlikely. For example, one "true believer" website offers this photo as evidence of stalks that were "bent, not broken":
They helpfully label the picture as "node bending". That looks sharply kinked enough that it wouldn't be out of line to call them "broken". "Bent" implies a more gentle transition.
Another "on the scene" report from another circle observes that "The oat stalks bent at right angles. They weren't broken." Maybe it's just me, but "bent at right angles" sounds like a broken (but not snapped) stalk.
Meanwhile, here's a photo of an indisputably man-made crop circle:
Now *that's* clearly "bent, not broken".
Some crops have undergone chemical changes, or show evidence of being under extreme energy burst.
According to whom, exactly? There are a lot of urban legends surrounding crop circles. Almost all of the wilder claims about "chemical changes", etc. trace back to W.C. Levengood, who's rather a crank on the subject. Double-blind attempts to reproduce his "findings" have been unable to do so. And some of his "findings" fall into the "no duh" category, like noting that seeds from flattened "crop circle" plants are often stunted if the crop circle appeared while the crop was young. Well no kidding -- squashing over crop plants is hardly do wonders for their health and productivity. Fold over your rose bushes and see how well it makes roses in three months.
I've seen all the plank and string guys, but a lot of the circles still show signs of having been exposed to something altogether different.
A lot of the "signs of having been exposed" etc. are urban legends, sloppy science, etc. And after the first few reports about "strange radiation" and so on, I wouldn't put it past pranksters to start spraying bleach or whatever on their works so as to keep the True Believers freaking out.
Article written by a prankster, detailing how the True Believers will see what they want to see, and overstate the difficulties (also a passage about not leaving footprints): Crop Circle Confession.
Sensible column about crop circles: Straight Dope
As for the "chemical changes", etc.: Overview of Levengood's results.
