Momentos - What's the Point?

I recently responded to a Tweet from @ADadCalledSpen, who also blogs as Dad and Proud, or That Spencer Bloke. (Way to confuse me there, mate.)
He was mentioning that even though some of his kids' photos are blurry, he was torn about throwing them away. Most of the commenters on Twitter agreed with him in some form or other, and I have to admit, I've been there. I remember the first official portrait we had done of the Queen(ager); even though some of the proofs weren't brilliant, I hated not to buy every single one because it seemed like I was, in effect, throwing her away. Nonsense of course, and I didn't succumb to that oh-so-obvious manipulation of the parental heart strings.
I have Tupperware boxes by the erm, boxload, of kid memorabilia. Until they're about ten, they come home at the end of the school year with giant trash/bin bags of every last thing they did during the year. Even though I knew most of it would be sums and stuff, I still felt obliged to go through it and keep the "special" bits and pieces. Admittedly, with child number three and dwindling shelf space, the 9 year old's bag comes in through the front door and straight out the back.
Every so often I try to cull; I find that with a gap of a year or more, I more readily ask myself "Why did I keep that?' Now I find that if I ask "For whom am I keeping this?" it helps too. (Not that I talk to myself like that but "Who am I keeping this for?" didn't quite flow.) It also helps to ask how many times, in the last five to ten years have I actually looked at the objects or shown them to someone else. Usually, they sit there year after year, daring me to throw them out and follow my calling to the Unfit Mothers' Club.
One thing that spurs me on to memento minimalism is the fact that, at some point, they will be handed down to my children, who will probably do the same as most adults when handed a pile of their kid crap - throw it out. I remember the year my in-laws drove a load of boxes a thousand miles to our new house. The boxes contained tons of the Ball & Chain's stuff, most of which he had no memory of and the rest he didn't really care about. I think I kept more of it than he would have, but it definitely served as proof that you really can keep too much.
Anyone else agonize over this?