I guess I didn't describe myself plainly enough. What I mean is that it should be just like Flash, working inside an HTML page right from any tab in your browser, no extra 'install' - except a full VM instead of a Flash instance.

If an application (some accounting program say) comes in Windows, Mac, and Linux downloads and is supposed to be downloaded and installed, but works fine if you install it in a VM with a plain image, why can't they put it on the web behind some HTML that asks for a jailed VM - and be given one? So that if you are on Windows, whenever you open that web site in a new Firefox tab, you use its app (right from that tab) in a few seconds without any (visible or persistent) install. Even THOUGH it is a native-only application that isn't built around networking (requests over http) nor any kind of internet technology like javascript. It's just a local program.

If the 'just a local program' could live just as happily in a new tab in a vanilla base-OS, you wouldn't need to go through installing it to try it, or uninstall it if you're not interested: this is where a 'web app' shines. Getting to the first screen takes less than one second (click the link you heard about it from, including on a Google search) as opposed to 15-45 seconds minimum to click through Download, Save, wait for it to download, Double-click in Downloads window (hopefully still in foreground) to open, Click 'Install', click 'I accept' click next, click next, click finish. Click OK and hopefully run now. (If there is no 'run now' then click Start, click Programs, find the new entry, click it.

Likewise, after you see the first screen you can say 'No this isn't what I had in mind at all' and click Back in your browser or close the new tab: 1-2 seconds. On Windows uninstall is: Click Start, Click Control Panel, click Add Remove Programs, wait for it to load, find the program, right-click, click Uninstall, click OK, wait for it to uninstall, click OK. (Or you could wager on whether they included an Uninstall icon next to their program icon in the start menu, but most programs don't).

If this web alternative were possible...then anyone could develop however they normally develop a native application (not app) - instead of having to turn it all into a client-server app or do it in javascript, flash, etc - and just let a user use it from their browser without 'actually' installing it. I guess my concept - since it is based on the usability of using something without actually-installing it (so that it goes into your normal start menu, for example) - is too nuanced for people, or I am not describing it right. :/