I think you are missing the point as well. Gnome and the web browser are about the user interface, not the "backend" code.
Say you want to write an application. Almost anything, say: computer algebra, screen writing, board game or sprinkler controller. You could write the interface in gtk or qt, or you could write it to the browser. Your backend runs it's own web server process, and you are instantly cross-platform, distributed and web appliance capable. Pretty compelling.
What is lost with the browser interface is the communication between subtle changes in your program state and the rest of the desktop, and communication between the browser windows. That's where gnome should concentrate.