We live in an age when our kids are more connected than ever before. We now live in an age when information travels around the globe in seconds and is on YouTube minutes after it happens. Kids now text more (14,000 times a month in my house) than call their friends and even I at 33 have to lot to learn about how things have changed since I was 16.
Social media like Twitter, Myspace and Facebook have changed the rules. We now proudly post what's going on in our lives more than ever, and the rules have changed since we were young and used to call the girlfriend for hours at a time.
The most important rule that you can remember as a parent/grandparent is that while your kid might have status updates on Facebook, you really don't have any business commenting on them. Keep in mind that the kid put the update up there for his friends, and having mom or grandpa commenting constantly on his wall is going to find another venue that you can't find to vent on.
A parent constantly on a kid's Facebook is like your parents listening in on your private phone calls (weren't they all private phone calls) and chirping in all the time. You know the type:
You "Oh my GOD! I can't believe that she said that!"
Your Friend "I know RIGHT, What was she thinking!"
Your mom from the kitchen, "What did she say?"
So here is what I suggest. Read your kid's Facebook/Myspace/Twitter/Friend Finder, whatever. Keep up with what is going on in his life. It's your job as a parent to know what is going on in your kid's life. He is putting a good bit of it up there, read it. However, don't comment on his wall. It is like the parent in the conversation above. Mom should make a note that there is something up with one of the kid's friends, but bring it up when you guys have time to talk to one another. You know, face-to-face. That's what our kids need more than anything else, our time. So if you are parenting on Facebook or using it to keep in touch with kids that you don't see much, maybe it is time to re-evaluate your relationship with your kid/grandkid.
He needs your time/not you stalking him on Facebook.