There's quite a good discussion going on today over on the Ex-Libris mailing list about some issues raised by David Hewett's article "Who Owns the Descriptions in Auction Catalogs? Copyright Lawsuit Looms" in the March issue of Maine Antiques Digest. Hewett's piece discusses a lawsuit currently in the works between Heritage Auction Galleries and Superior Galleries Inc. regarding what certainly seem to be examples of blatant plagiarism in several Superior catalogs of coins (Hewett provides a number of the cited examples so I'll refrain). Through its attorneys, Superior claims that the descriptions are not protected by copyright, but even if they could be, "fair use" would apply and allow Superior to use the descriptions as they please (they also offer nineteen other 'defenses').
I can't claim to be versed well enough on the intricacies of copyright law to know whether the descriptions are eligible for protection or not (although I tend to think they would be, given the broad protections that currently exist, for good or ill), but it seems to me just common courtesy that if you're going to use someone else's catalog description, the decent and ethical thing to do would be to cite it as such. Sure, there are going to be times when a prior description is most appropriate (whether it's the same item appearing at a later auction, or simply an identical piece). It really isn't that onerous a burden to provide a citation to another description from which a section is being quoted, is it? Granted, coming from a history background and being inordinately fond of footnotes maybe that's easy for me to say, but I don't see the difficulty there.
Outright use of someone else's work without credit is, if not illegal, certainly unethical and not particularly pleasant. It shouldn't require a lawsuit to teach us that.