Parenting question

Over at Marginal Revolution, Tyler Cowen asks "Why do parents talk with their children's friends?", and provides a bunch of possible motives.

I certainly want our four year old to bring his friends home, and like it and encourage it. Of course, he is at an age that he doesn't care about things like privacy and stuff, but I certainly hope he won't mind -- nor resent -- our getting to know his friends and chatting with them when he is a teenager.

I think the trick is to keep inviting his friends to come to our place and play, talk, sing, dance, etc. for all time to come: childhood, adolescence or adulthood. Rebellion and resentment arrive on the scene only when we ignore all his friends now -- the 'safe' stage -- and start taking an interest in them during his teens. Now that I think about it, this is what my mother did! And, I don't think any of us resented it. Of course, she also had this great knack for making people feel comfortable in our home. Now, this is something I have to work on!