The day Bitcointalk allows animated signatures, is the day I'm going to enable "Don't show users' signatures".
Once in a while I see "the internet" without Adblock Plus and without "image.animation_mode once", and I hate it with a passion. I'm okay with some ads and some animations, but it quickly gets overused.
It seems that I can already imagine the flashing animations, big Comic Sans Letters and RGB action in signature, replicated by x amount of users. The readability of the forum would quickly become impossible without some kind of blockage, thus defeating the purpose of the signature campaigns.