I get your point, and I think it's a reasonable point of view. I guess my belief is a little different -- I feel like people are fairly bad judges of what something is worth culturally. Sure, we get the high points right, but the Internet is chock full of stories of undiscovered genius that nearly ended up in the trash bin. See for example http://www.messynessychic.com/2013/02/18/found-at-auction-th...

Soundcloud contains an incredible collection of sound clips. If you take the virtual bulldozer to it, then you're just increasing the chance that something of value doesn't get copied over to archive.org or freesound.org, because the original owner isn't willing or able to do so.