Oh, I got caught at that top-o'-the-hill dumpster! I loaded up a few boxes, set them aside, and when I came back to fetch the second one, dude saw me, asked "Did somebody say you could do that?"
I told him no, that I was just concerned about global warming and recycling and such, and he told me "Yeah, but we're trying to sell that. It's like you're stealing." What a dumbass. I just kinda said semi-sympathetic "Yeah. Yeah..."s as I walked away with that box.
So when was that when you noticed the lower dumpster start being locked? I'd say that must have been around this time last year; were you still in Seattle then?
Interestingly, every time I come to Seattle, I again find it locked, but before I go it gets irreparably unlocked...