I find it interesting that Google, in all their might, still consider the reasons for targeting web apps to be (at least in part) economical:
I mean, if even Google balks at the cost of multiple client platforms (mobile and otherwise) what hope to mortals have?
Thus for many things web apps (as opposed to web sites) are the future. I am sure there is a kernel of apps that require desktop presence for the time being (video and audio editing, development for example) but otherwise, it looks like we have to look towards web tech for the future of client side computing.
