So here's what I got out of it: Videos, and probably the extension, are *technically* prohibited by this ToS, unless they make a specific exception. Now, they're almost certainly not going to care, but they need to technically explicitly say so.
I'm fully aware, Polk, that it LOOKS like the first paragraph I posted here is referring to things posted specifically on their site, given the previous paragraph. But that isn't made explicitly clear, and, well, IANAL.
Second paragraph, section ii and iii seem to be the real problems.
I've also posted a thing about this on their forums - they haven't gotten back. Also, there was a post within the last day where someone was saying that the extension isn't working and their response was on the order of "We're not responsible for 3rd-party stuff, I'm sure they'll fix it soon," which seems to imply at least tacit acceptance of the extension.
Videos are, at least potentially, another matter though.
I doubt anything will come of this, but I always find ToSes kinda stupid, mostly because I always actually read them (and they're all more or less the same drivel).