The vision of presenting art history on the terms set by the Internet had made good sense to us. It looked like the perfect medium for unfolding the paradigm of diversity. But then we came up against something that limited our options: copyright.
— Merete Sanderhoff, curator of digital practice at the National Gallery of Denmark, in Sharing is Caring: openness and sharing in the cultural heritage sector

Merete continues,

The costs were tremendously high. Just one image cost several hundred dollars, and that would only buy us clearance for a limited period of time. The labour involved in writing to each rights holder, asking for files, describing the intended usage, and so on, turned out to be a major drain on our manpower.