But the concept goes beyond Mobile and we see it coming to Web services. 

Websites that have an API on which developers have created applications are also gathering those apps in an "App Store"

A directory of apps has also a legitimacy since those websites are also platform. Here are a few example

• Facebook: you could consider their directory of apps like an App store
• Twitter: they did not gather 3rd party apps, but OneForty.com has done it
• WP-Plugins: same thing here, this time for Wordpress plugins, they even say it in their logo
• Flickr: they recently launched their App Garden. An app store of Flickr apps
• Zynga: is slowly but surely becoming an App Store for games, and very much looks like one

Who could also call it App Store? Firefox with all their plugins. Boxee wants also one and is getting developers to build their apps (this one is interesting because hardware is getting involved, like on the iPhone)

• The difference with Apple App store? there is not always an clear business model and payment system associated to them.
• The common point? Users want to a simplified access to services based on simple task-related apps 

App stores are a clear trend. Directories are back. Mobile and Web together