Matt Bors has an interesting item about The New York Times and its policy regarding editorial cartoonists: it seems the paper Photoshops out their signatures before running them in the paper. I'd never heard of such a thing, but commenters on his blog say that it's not a policy exclusive to the Times. Matt notes that many of the cartoonists have won Pulitzers for their drawing, and asks:
Would a Pulitzer Prize winning columnist be asked to put up with this level of ineptitude and insulting treatment of their craft?
I agree with him, but I'll bet that the Times (and other publications) consider editorial cartoons to be the equivalent of photographs or graphics rather than columns, and graphic elements take a standard credit line instead of a signature.
Nevertheless, I'd say that the artist's signature is an element of the drawing and shouldn't be retouched out of existence, any more than an element in a photograph should be retouched.
I wonder if they'd do it to, say, a Hirschfeld?