Probably most people don't notice or care, but Facebook introduces so many artifacts into jpegs, there's got to be room for a startup that actually doesn't compress the crap out of images.
flickr is actually quite popular amongst my photographer friends; artists and doodlers seem to use deviantart.
Facebook is a place for photos of people's faces, really. If the artifacts prevent you from seeing someone's face, the picture is probably too small to begin with. Putting other kinds of photos on Facebook (like, say, Cinnabon(TM)) always baffled me, but people do it anyway.
The average Facebooker doesn't know what that is and doesn't care. Just like so many people listen to music on iPhone or laptop speakers, quality seems to no longer matter.
Music on an iPhone with headphones is probably better than what 90% of the people in the eighties/nineties ever heard.
CD systems' speakers (when not Hi-Fi) have worse sound than middle of the road headphones, and cassette had like 8 bit definition (and noise, wow, flutter and other nice stuff to degrade the sound).
with increasingly decent phone cameras, and everybody seemingly buying a DSLR to start a "Johns Photography" page, facebook will have to respond to this - currently their compression is horrible
