I have noticed that ponies in particular suffer from "the grass is greener" syndrome. We use the same temporary fence for 18 ponies (literal ponies, not 14hh ponies, little evil brat ponies), and our two horses. The horses look at the line and say "well, that's disappointing." And go about their business. The ponies see that line and say "Whatever is over there has GOT to be better than what I have over here!" and they do whatever it take to get there.
So I'll be watching this post closely because I'm sick of chasing those dang ponies all over creation!