Due to recurring problems with scaling of large animated GIFs taking down the image scaling servers, we put in a hack to prevent server-side scaling of very large, then *all* animated GIFs.
Unfortunately this currently applies to *all* GIFs, which can be very nasty for cases like this page:
This category on Commons has a gallery with a large number of scanned pages... uploaded as large GIFs... which are not being thumbnailed... so they're all being loaded inline...
My Firefox process was using 2.31GB of real memory after loading the page. Not so bad when you've got a loaded 4-gig box, but pretty crappy if you're on a more typical machine which will keel over and die.
We need to distinguish between animated and non-animated GIFs so still images can continue to be scaled cleanly.