How do you feel about kids' sleepovers?

Last night my middle son had a friend come over to spend the night, at midnight his friend couldn’t hack it anymore and I drove him home. That got me to thinking about this topic and wondering if sleepovers are the norm.

In general my kids love spending the night at their friends’ houses and love having friends spend the night with us. I did this some when I was a kid, but not very often. If my kids had their way they would have sleepovers every weekend (weeknights too during summer vacation)! Did you have sleepovers much as a kid? Parents how do you feel about your kids having sleepovers?