Honestly, the only reason I thought about it is because I've been saving .jpg files with no less than 96% quality over compression for at least three years now. So when images that aren't but eight months to a year old start looking like I saved them with MS Paint or something, I have to wonder what's going on.
I mean, I don't know for certain that the host is to blame, as I haven't found any originals floating around on my drive yet to use for comparison. But it seems that way, and it sounds like I'm not the only one who has experienced this before.
Oh, and off-topic, I kind of seriously love your username and drop box .gif.