What features make a smartphone "Smart"?

I suspect that most people's first answer would be 'internet'. Well, there are plenty of 'feature phones' (aka. Dumbphones) that can still pull up a page from the web or connect to email accounts. I think a phone can have a web browser and still not be a 'smartphone'.

3rd party applications? Well, I'm not sure if I would go with a definition that would rule out the original iPhone (and again, there are applications available for phones that I wouldn't call 'smart'.) But this feels a bit closer to a real point of differentiation.

But I think the important point is perhaps a little less obvious…