William, its just to give you a much better option to identifying script
files. Basically if you just provided a key string, this will surely make it
unique but if the key was associated to a particular control, it wont clash
with other controls that might be using the same key to identify their
scripts, since now my key is prefixed to my control.

Specially if you are a control author, this is useful since I dont know what
kind of key the end user  might want to use to uniquely identify his other
script files. I dont want to assume what it might be either, so if i can
prefix this with the type of my control i have a better chance of making the
key unique and avoid any un-necessary clashes or limiting the end user. I
guess you can consider specfying a type as providing a namespace.

This is also hinted in the documentation :
"A client script is uniquely identified by its key and its type. Scripts
with the same key and type are considered duplicates"

Regards,
Alessandro Zifiglio
http://www.AsyncUI.net