Web Apps vs Web Sites
From Standard Pixel:
Indeed we are becoming more and more aware that there are two different categories of web project, Web Apps and Web Sites. Web Apps are a lot like a desktop client. Users expect to have a single interface and be able to get to everything they need in few clicks. Web Sites, on the other hand are more like a news paper and people expect to enter through a front page of some kind and explore in to get more detailed information on a subject. For me, I have settled on creating one Web App project with a Ruby on Rails back-end mixed with a client written in SproutCore. Another project however, is a simple information site which will use PHP, along with a little interface help from YUI. - SproutCore is a chainsaw and YUI is a paring knife.
Could not agree more. We decided a long time ago that there is a big difference between building a thick-client JavaScript app vs a web site with some JavaScript enhancements. Thick-clients require a whole new level of complexity that web sites don’t have. Use the right tool for the job.

fyi, the link to the standard pixel blog is pointing to sproutcore.com/blog.standardpixel.com
It’s interesting.
Flash and Java were intended as “web app” foundation before, and failed. People did not like sandboxed apps which did not mesh with the rest of the internet (search engines, bookmarking, etc.).
“web app” needs not be a sandboxed single page - in fact I would say this is not a web app at all. This is something (an app) that runs in a program, which happens also to be a web browser.
A web app should mesh with the web as much as possible.
That is not to say that “thick-client JavaScript apps” (as you describe them) are not useful. They just don’t get any benefits from the web. They could be flash or java apps. And such apps did not work out well in the past. Light-weight web clients were much more successful.