It's irritating that people use a low-quality image format all the time!

I don't understand. It makes your images look like crap, and it's even more so annoying when you save an image I drew and you save it as a JPEG and then post it and expect me to edit it (Kind of like that land-of-us thing).
JPEG is also annoying because it can't be transparent.
So discuss your hatred for JPEG and JPEG artifacts