I'm currently having my own issues with this. The other day I loaded a quilt backing onto my frame. I didn't have time to do anything else right then and left it like that. When I went back the next day, I could see a huge dent in the fabric all the way across the room. I stupidly left the door to my sewing room open and my heaviest cat, David, decided that would make the perfect spot for a bit of a nap. It probably made a good hammock. Imagine how much a 20 pound cat can stretch out a piece of fabric. Now I'm in the process of trying to quilt it without huge puckers on the back.
I'm about half way done with the quilting now and hoping you won't be able to tell anything happened. But I've learned my lesson. My quilting room is barred to anything with a tail whenever there's a quilt on the frame!
"A fool gives vent to his anger but a wise man keeps himself under control."
Proverbs 29:11 (NIV)