In many applications the window represents a document in the application, while the application itself doesn't have a window. In OSX it is very common for closing a window to not remove the application from the dock. This is, of course, highly cynical, and breaking native OS convention in this fashion is extremely bad practice.

Most Windows users don't have visibility of any applications not on the taskbar, so by hijacking the close button in this fashion, Skype can ensure that there's always peer-to-peer nodes available to handle new calls. This means that, as a Skype user, your machine is being used to facilitate other people's connections even when you aren't making a call yourself, much as a BitTorrent user is serving data to other users when he or she isn't making a download themselves.Īs such, it's not in Skype's interest to allow users to easily close the application, as that means that more traffic has to be handle by Skype's own servers, which naturally comes at a cost. Skype, being a peer-to-peer telecoms application, works much like BitTorrent and other P2P distribution methods by relying on users' own machines and internet connections to route the traffic of other people's calls.

Itunes minimize to taskbar