> my wife walks up to my computer and makes a copy of the data
As you agreed to in our contract, you now need to compensate me for the damage caused by your failure to prevent unauthorized third-party access. Of course you're free to attempt to recover the sum you have to pay me from your wife.
> The output of a program is rarely copyrightable by the author (as opposed to the user).
The author of the program can make it a condition of letting the user use the program that the user has to assign all copyright to the author of the program, kind of like "By uploading any User Content you hereby grant and will grant Y Combinator and its affiliated companies a nonexclusive, worldwide, royalty free, fully paid up, transferable, sublicensable, perpetual, irrevocable license to copy, display, upload, perform, distribute, store, modify and otherwise use your User Content for any Y Combinator-related purpose in any form, medium or technology now known or later developed." https://www.ycombinator.com/legal/