As you should know by now, the Internet never forgets. Go to the 'way back machine' or even google for old articles and you can find things online that predate the internet. Or pictures you thought you deleted from that wild 'shopping' weekend with friends!
So how do you think your kids are going to react in 10 years (or less!) when they get their own Facebook page and see all stupid pictures of them that you've posted over the years? Or when their siblings beat you to it and tag them, for all their tweener/teen friends to see?
Just saying ;-)