Actually, my current thinking is that there are three (or more): one that’s an extension problem (linky, perhaps?) that’s the bulk of what I’m seeing, one that I’ve filed as Bug 342802 that was messing up my testing (because I’d see a huge leak early on, and think “Oh, that must correspond to my giant leak in normal usage!”), and a few more small ones that make it so I can’t just open the browser for a few moments, check leak-gauge.pl and see if anything leaked, I have to actually leave it open for a long time and use it to see if the leak was big.

So yeah. I don’t feel like spending a few hours testing each extension, so maybe when I feel more motivated I’ll look into it again, or maybe it’ll just fix itself if someone else sees it.