Guilt

Why is it that the simplest, and often the stupidest things can trigger the most guilt? Is Mom guilt genetic; something that kicks in upon giving birth? That makes sense to me as I don't remember reading in my Dr.Spock or 'What to expect when you're expecting' anything about the importance of feeling guilty. Yet almost all of the Moms I know feel guilty about something. Of course if it is generic how do you explain all the Moms who never feel guilty about anything from benign neglect to out and out endangerment? Maybe it's socialized somewhere so deep in our brains we don't even know its there?
So my latest bout of guilt was triggered by the paperwork for the senior year book. Yes the yearbook; I told you it was stupid. There are pages in the year book entitled Then and Now. They are filled with pictures of your kid with his friends at a young age juxtaposed with the same group at ages 17-18. It's a very popular section. However, my kid entered the district in 9th grade so we have no Then pictures. Looking over the section my heart broke and I felt like I had completely let him down.
When I finally got up the courage to go over the paperwork with him and explain that I didn't think we could do this section he,of course,could care less.
Forget the swine flu vaccine, can someone invent a vaccine to stop useless mother guilt?