The problem with mathematically calculating Flash wear is that it simply does not work like that. File systems like FAT and NTFS are not designed to be used on Flash! They make constant writes to the same location, over and over, sometimes racking up hundreds of writes to the same location every minute (defraggers, for example). Typical file systems will very quickly wear out a Flash device, as evidenced by the constant failure of Flash memory cards and USB sticks. Some people have tried (and in the case of Linux, succeeded) in creating a Flash friendly file system that tries to spread out wear across the device. But since Windows can't read those file systems (without additional software), they aren't commonly used. Instead, people continue using the good ol' FAT file system for most Flash sticks, wearing them out in short order when most of the other cells never see much action at all.
Sssssoooooooooo.... long story short, Flash is more susceptible to damage than most people seem to realize. That's why it's so important to run a write filter on any Flash device (and I think EWF has a lot more potential than FBWF since it prevents even filesystem maintenance writes - the worst of them).
If only EWF weren't so buggy... :(

