To answer your point

“does exposure of hi-res pictures stop people from buying them?”

I would say from my point-of-view part of the fun of visiting a museum/gallery/etc is going to the gift shop!

The ability to print off images myself doesn’t appeal to me in the slightest; however being able to blog, or write about said trip to a gallery with image links of favorite paintings etc. – now that would be really valuable for me.