Tanveer Badar asks why the file properties Advanced dialog shows two checkboxes (compression and encryption) even though NTFS supports only one or the other at a time. "Why not have two radio buttons instead of these silly check boxes?"
Actually, if you want radio buttons, you'd need three, one to cover the "neither" case. Let's look at what those radio buttons would look like:
Compress contents to save disk space
Encrypt contents to secure data
Neither compress nor encrypt
This takes an implementation detail (that NTFS currently does not support simultaneous compression and encryption) and elevates it to the user interface, so that it can provide maximum confusion to the user. "What a strange way of exposing compression and encryption. If I want to turn on encryption, I should just check a box that says 'Encryption'."
The current implementation (two check boxes) matches user expectations, but then says "Sorry, we can't do that" if the user picks a combination that is not currently supported. But who knows, maybe someday, NTFS will support simultaneously encryption and compression, and all that will happen is that the error message goes away. You don't have to redesign the property sheet (and invalidate all the training materials that had been produced in the meantime).
Either way, it's a leaky abstraction that sucks, but at least the suckiness isn't shoved in the user's face.