I taught myself to program when I was 12. I didn't have any books, or anyone to turn to for guidance. If I could do that, I think its perfectly reasonable that at 6 or 7, my son could start to pick up the basics if he so chooses. And if he's not interested, that's cool too.
Thanks for your helpful input but contrary to your expressed sentiments it's not obvious to parents that 5 is too young. My 3 y/o is able to easily navigate the ipad and the computer, play games, find and start movies, etc. I wouldn't be surprised to meet a 6 year old who understands basic programming expressions.