We should definitely not be throwing away old computers. They're just as useful as they were when they were assembled, and can be tasked to do all sorts of things we haven't even thought about yet.
I'm a huge fan of retro computing (Oric-1 Atmos, FTW!) and there is nothing more satisfying than to sit down and download a fresh new app, built this year, to run on a system built 30 years ago. I think this is a feeling that must persist, somehow, so I encourage everyone and anyone who has an old computer in their attic to dig it out, boot it up, and keep it running. Even if you can't find a use for it, there are a million other people out there who could. Give it to the kids and let them learn computing in the most distraction-free environment you can give them... my kids learned computing at the 8-bit level and its already put them way ahead of the iPhone-addicted peers. Sure, the Oric may not have the latest and greatest titles, but at least my kids know how to put a picture together with nothing but a few characters, an editor, and an understanding of hexadecimal ..