I wouldn't use what other parents do as a guide for what you should do. All it takes is a quick look around to see that most parents in the world today, for lack of a better term, "suck ass." Sure, all her friends parents are getting them thongs, and they're probably all going to be having sex by 14 or 15 since their parents clearly have very little interest in regulating their child's sexuality. And this coming from a libertarian-leaner.
And just to echo BOR, this is really a good thread to read:
http://www.tfproject.org/tfp/showthread.php?t=46915