I think that eventually, you WILL hear people say just that. My best example would be when i visited the National Cathedral in DC. I loved the gothic architecture and inherent beauty of the place, in particular, the intricate stained glass windows. The only problem was that the windows are usually about forty to sixty feet away, and I'm afraid I was without my trusty binoculars.
I would really love to see web pics of these windows, so that I could zoom in and closely see the detail that the artisans put in to make them as beautiful at a distance.
You are right when you say that viewing art over the web has the ability to cheapen, but only if it is the sole method used by the audience.