I remember when the PC was first attached to the Mainframe using a 3270 card I took a job working on a project (PC/G) which would allow you to do all the PC things on the mainframe using a "smart" 3270 protocol (TCA). I even demo how to run space invaders on a mainframe via the PC... It was not a great success to say the least. The browser can do everything argument reminds me a lot of that old TCA protocol, it looked at the old model of doing things (mainframe) rather than the new (PC). We are in danger of doing the same thing and thinking of the old model (internet) rather than the new (devices such as Xbox, Zune, VOIP Phone, Mobile phone, Media centers etc). There will of course always be the internet as there still is the mainframe, it just wont be the center of our universe.
This is also why I hate all the hype over Ajax, to me it is the same as the extended 3270 datastreams which allowed me to run mainframe space invaders in the terminal PC. I could do it but it was hardly very sensible. This makes me very dubious of all the "write once, run anywhere", "one size fits all" and "Ajax can do everything anyone can ever want" arguments.
As I have said before with software you can do anything anywhere, the trick is to do the right thing in the right place.
Why is this so hard for some people to understand?