Ralph Blumenthal and Tom Mashberg have written on the issue of objects that do not have full collecting histories ("The curse of the outcast artifact", New York Times July 12, 2012). Collectors are finding that they are unable to donate their objects to public museums. Among them is Alan M. Dershowitz, the Felix Frankfurter Professor of Law at the Harvard School of Law. Dershowitz wishes to sell an Egyptian sarcophagus purchased from Sotheby's in the 1990s (a period explored in Peter Watson's Sotheby's: Inside Story) but he "can't get proof of when it came out of Egypt".
Interestingly the NYT cites the seriously flawed study by the Cultural Property Research Institute (CPRI).
Among those interviewed is William G. Pearlstein who asserts that the lack of a collecting history is not necessarily significant. However, the Medici Conspiracy has taught us a great deal about how such objects entered the market.
It is perhaps significant that Christie's are reported to have made the claim that they do not sell Egyptian antiquities "unless it was absolutely documented that it left Egypt before 1970". This seems to contrast with Christie's attitudes over antiquities that can be traced to the Medici Dossier.