Well... Surely I don't like the idea of a digital signature but, to be perfectly honest, a lot of highly prestigious artists do not sign their prints and they sell very well, sometimes by outrageously high prices. Actually some artists consider signing a childish act or something people do to make a statement, something like "This is art! Look, it is signed and numbered, so it must be art (doesn't matter it is a cheesy obvious shot of the sunset on the desert)."
I do agree that this is true a lot of times, but it does not invalidate the concept of signing. I do hand-sign all my prints.