This first came to my attention with digitoxici, where I am ashamed to say I stripped a few perfectly valid source-tags due to my general bias against textual sourcetags. It seems there are a few other artists who also do this.
Something I'd like to do is standardize cases where the uploader IS the art's source and set it up so that other taggers can sourcetag appropriately when this is known. I propose a standard of using "uploader" (without quotes) in these cases.
Updated