Kriston Capps has a long post on the issue of collector-founded museums, discussed recently here. To his credit, he seems to recognize it's a complicated issue. For example: what would happen if we crack down too hard on these museums?
"What if the Kreegers hadn't seen any incentive in turning their home and art fortune into a museum for the public? What if it didn't make sense for Duncan Phillips, or Henry Frick, or Alice Walton, or William Corcoran? One alternative is every art lover's nightmare: collectors who buy artworks and never show them at all."
The whole thing is worth reading.