Consider for a moment the perfect separation of client and server in that example. Only one machine needs to have that EXCEL creation code installed on it. IIS running as a web host handles firing up these web methods whenever they are asked for by a client. This can be a browser. This can be an Android app. They run on separate threads associated with the AJAX POST they get from a web page, for example.

The client code is run in a browser - so you have no install needs for client access. Sure I tell my clients to use FireFox because my JavaScript is debugged against FF - I know it can handle the really huge ARRAYS I am putting in place from these AJAX calls.