How Small Can Gadgets Get?

It’s great that our communication gadgets are getting smaller and smaller, but our hands are not. At what point does it become too small or no longer usable for a PDA, smartphone or other device to shrink?
I’m not one of those Blackberry wearing, Smartphone clicking guys but stick (for now) to my basic PDA (Palm Tungsten E) and notebook computer from Gateway.
News Factor writes “When it comes to miniaturization, the Audiovox Latest News about Audiovox 5600 smartphone is already pretty small,” observed IDC research analyst Dave Linsalata. “The question is whether going any smaller would make for a usable device,” he muses.
“You can shrink a keyboard, certainly, but unless you are shrinking people’s thumbs along side of it you are going to run into a usability problem,” agreed Research In Motion Latest News about Research In Motion (RIM) vice president Mark Guibert.