Here's a video of him stating the change:
http://www.youtube.com/watch?v=57t2TUu_LVU
I think it's a pretty classy way he went about it. He explained his reason but cushioned the disappointment (if any) by doing photo ops and being pleasant and very approachable about it. The video's poster is obviously a dealer as he says he has previous autographs for sale.
TTM won't be much of a loss IMO as I'm pretty sure half TTM were secretarial (photos provided by his office) and half authentic (sent by fans).
Will be interesting to see how this progresses as he says he won't sign his books either. He has a lot that have been published and probably has more coming so I wonder about book signings as he's done them in the past.
I'm not quite sure all the big time stars who still are as active as Bill Cosby but there are some big names still around that are near impossible to even get near. Hopefully he will continue with this trend and be as approachable as he seems in the video.