Compression of files to create a zip archive. Primarily to be used in scenarios like :
we write a couple of files to the Isolated storage.
We let the user save a couple of files ( with the help of a compression library (classes like ZipArchive, ZipEntry etc...)).
These files can then be zipped up into a single file for the user.
When a silverlight application needs to output another silverlight application (rarely)
To be short, a compression library similar to the one in Infragistics or ComponentOne.