There currently isn't. It's entirely doable; I know it's an option to display this using GSAK and FindStatGen, I used to see it when I'd display the "finds by owner" stat section. I'd support having it added to the stats.
As far as making it a karma stat, I hadn't thought about it before, but I guess I'm mildly curious now. So, sure, I support adding that, too, as a lower priority than total unique cache owners.
(It could even be added to the badge system...)