Why do you feel you need to get rid of some? I don't think I could do it! I'd just keep them somewhere separate. But when you're old with lots of time just hanging about, you might want to look back over all of them? Write the most detailed and well illustrated memoir ever?? The kids might want to see them? Or they might become famous and others might be chewing at the bit to find out their history? It becomes a national treasure! Some sort of potential alibi or clue for a crime in amongst them??!! Future generations piecing together your life through photos?

>strange attachment to photos right here<
I also wouldn't get rid of them, what you might pick now as being keeping worthy might not be what you are interested in, in the future. Storage is cheap these days. When I look back at my parents photos - lots of the ones that are most interesting, probably wouldn't have been classed as good photos, some are just a blur - but they bring back memories they are a trigger for remembering.

Within Picasa their is a 'star/favorite' feature - so I tend to just star the ones I really like - so if I only want to see those then can just click 'show starred' lots of the photo organisation apps have something interesting.

Some of my pics I GPS tag, and they are all automatically date tagged - so they are even more useful for reminding of things even if the picture itself is not great.