"I imagine it would have some value if the author was troubled to paint each autograph uniquely prior to upload. That could certainly be a technical possibility that could be enforced."
And there already exists suitable technology1 to get a 'proper' autograph in electronic form: Touch screen devices - preferably with a stylus, but I suppose with a little practice authors could develop a finger-written autograph.
So perhaps a better solution would be to develop e-readers so that they could go into 'signature' mode, whereby the device can be signed on screen and that signature (image produced by the author signing the device) added to the file so that it's always displayed at the start of the book.
As I said, the technology for accepting signatures this way already exists in software - and the hardware clearly already exists. My idea is purely to implement this in e-reader software - so, come on Amazon, Google, Nook et al, piss on Apple's fire by doing a better job with this idea.
Just don't patent my idea and claim you invented it, you greedy, thieving bastards!
1. The most commonly recognised implementation, I'd guess, is the PDA and stylus combo carried around by some delivery drivers - instead of signing a piece of paper, the person accepting the delivery signs on the stylus2.
2. Based on my own efforts, though, the big flaw seems to be producing a signature on those things that is anything like the real thing. :)