Few, because when tasked with a problem that this could solve, most people would immediately throw up their hands and give up. This is the biggest obstacle of all.

"Which pictures are you missing?" "I don't know, I'm not going to flip through them all!"

(This happens more often than I'd like to admit)

But what about a slightly different one? E.g.

I have two folders, each a bunch of files. Are there any files that are not in both folders?

edit: I did not know this- I just posted it because it is but one answer. For what it is worth, I agree with you- basic knowledge of programming is something everyone should know.

A lot of my coworkers.

They take a screenshot, thus offloading the hard part onto everyone who needs to get data out of their email.

It's about as awesome as it sounds.

At one point, the general mgr of our office, said that these things were so valuable to everyone, and I was so good at it and seemed to enjoy it so much, that he was wondering if it wouldn't make more sense for him to take me off of my own consulting cases and make IT projects my only case. Of course, IT people were thought of as lowly support staff for the elite consultants, so it would mean a pay cut and end my consulting career. This wasn't a warning; he was just thinking that this might better serve the needs of the firm.

That day I stopped being a valuable IT resource for my coworkers and reserved my dev skills for my giving myself a "sustainable competitive advantage" in my own work on my own cases.

The powerpoint extensions I used in consulting were created by ex-consultants so it's not unheard of to do this.

As far as the hard part goes, I'd think an OCR script could handle this even if they're using Comic Sans for their file manager font.

And yeah, that's an option that I've considered it in the past, but never been able to validate it because it'd take me less time to just transcribe it (or I can find a glob pattern from their screenshot, etc.).