There are many cases that justify when to use and when not use sound on the web... I would say it's the goal of most web-app builders to mimic desktop apps b/c

There are many cases that justify when to use and when not use sound on the web... I would say it's the goal of most web-app builders to mimic desktop apps b/c the result is a familiar environment for the end user. Software/UI design is an established practice, with many studied and proven methodologies for handling complex user interaction that has been unfamiliar to the web in former years. That said, I believe it's inevitable that web-apps will mirror their desktop counter-parts in time (many are doing so already)... the exception being, highly-specialized web apps.