Saluki - my children are entitled to very little privacy until they are 18. Until they're old enough to be legally responsible for their own actions I have a say in the decision making process. This includes my college aged daughter that returns home for the summer. I have never felt the need to read their notes, look on their computers, check their phones, but that isn't to say I wouldn't do it in a heart beat if I thought there was a problem. This isn't an invasion, it's called parenting.
I am fortunate, I have excellent kids and they generally make good decisions. But that isn't all luck, a lot of it has to do with the way they were raised and the morals we taught them.