Of course, just because *we* know how to contain and control it doesn't mean we necessarily will in a few millenia. If something happens to wipe out humanity's technology we'll end up with these nuclear waste caches across the globe. And, honestly, I don't think this is a big problem - for one thing it's not like they're going to be covering an appreciable amount of the earth, and for another thing there's more dangerous areas in nature itself already. (Bogs. Quicksand. Poisonous animals. And so forth.) If NextHumanity can't learn to deal with a little radioactivity, they're doomed.
All that said, though, it would be nice to warn people away for a while. And that's what this talks about.
I've got to say, these ideas? They're fucking awesome. Not in the sense of them being useful - but in the sense of post-apocalyptic relics! These are exactly the kind of things you'd expect to find trudging across the blasted sterile soil of America after World War 4.
Reality's awesome. It's so similar to scifi.