Blee,
reading your responce to my question , then yes you do need to worry a little, have you had no training or experience at all ?
so in answer to your question , yes carpets can pull off the grippers, carpets can shrink so my suggestion would be get your self out with another c/c and get some basic training and you will learn which type of carpet is most at risk, to give you a specific answer over the internet is difficult unless you already know the different fibres, constuction and type of carpets you are dealing with, and judging by your question you dont know.
Beware, now i,m beggining to sound like Derick
Geoff