I agree wholeheartedly, Frank, Raid and PlantedTao - I have always felt that documenting family life is one of the greatest gifts you can give your children (and your future self). I have felt this more stongly than ever since I became a father myself, and have always made sure I have pictures of all the generations of our family together whenever possible. At family get-togethers we have always tried to get pictures of my my grandmother with all of her great-grandchildren so that in times to come the children will be able to look back and remember her.
A note about posting family pictures online - I thought about this a lot a few years ago as I keep a family website. My father works abroad in Africa for most of the year, my sister lives in Brisbane, we are in the UK and have close friends in New York, Lisbon and other far flung places. The website has always been a very practical way to share family news and photographs.
The thought that there are monsters out there who wish harm to children is a sobering one indeed, but IMHO if we let that stop us from sharing and enjoying pictures with family and friends, then the monsters have won.
From a practical point of view, I would never post a picture on my website that I would not happily show to an interested stranger on a bus - or to put it another way, any monster viewing my site would see nothing more of my children than if they were observed walking along the street. To my mind, paranoia beyond this point serves no protective purpose and only limits our own activities, not those of the monsters.
Anyway, just my 2p worth, but I have always been comfortable with this decision.
Cheers, Dan