Imagine a line of business web app, where once you are logged in and use the app it downloads this. How is this much different from downloading a desktop app th

Imagine a line of business web app, where once you are logged in and use the app it downloads this. How is this much different from downloading a desktop app that needs to download a few meg of libraries. It definitely is not needed for blogs, wikis, news sites etc. This would be for web applications.