Why have I forgot more than I remember?

I've realized lately that I've forgotten more about my life than I remember.  I wonder if this is unique to me or does it happen to everyone.  The big question is why?  Were the memories lost so insignificant that they weren't worth remembering or did the ones remembered just take priority for some reason?  Why does our mind selectively chose which memories to keep and which to discard or are we telling it to do so without knowing it.

Einstein once said "You shouldn't clutter your mind with anything that you can look up elsewhere".  Well now, he didn't have the internet.  If his statement is true then we need not remember anything because it would seem the internet has remembered it all for us.  Except for the personal stuff that has never gotten posted to the net of course.  And, more and more, with Facebook and sites like it even the personal stuff is finding it's way onto the net.  One of the many reasons I don't belong to Facebook.

It's also strange that when talking to siblings about our childhood their memory of events is much different than mine.  Not just major events but also small things that I remember and have always thought to be accurate.  Now I'm not so sure.  And there isn't any way to absolutely prove who's memory is correct.  We were both there and had the same experience at the same time yet remember it totally differently. So we bring in yet another sibling and his or her memory is different than both of ours.  Is this only happening to me?

"Obviously the memories are not important or you'd remember them" says my wife.  Although I'm not totally convinced of that.  If they are not important why do I want to remember them?  This is nothing small you understand.  Who years and even larger gaps are gone from my childhood that I don't remember.  Places we lived, friends I had as a child, teachers, classmates, etc.  So much is gone and I'm only now starting to realize it.

No I'm not concerned that it's elderly memory loss because, as I understand it, when this sets in you remember the old stuff and forget the more recent events.  This is not the case with me.  It's like, in some ways, my childhood never happened or only happened in stages.  Weird............just weird.

Anyone else having this happen?