David Knell is a well-known collector of ancient oil lamps based in Hampshire, he has an attractive and informative website displaying his collection. He has recently added an introduction which I found worthy of note:
Policy The core of the collection was formed many decades ago and added to since. In the early days it was easy to be certain that the lamps acquired had come from even older collections but over the years it has become far more difficult to distinguish between those and lamps that might have been excavated more recently. Due to that difficulty and a desire not to contribute, even unknowingly, to a destruction of the archaeological record caused by modern illicit excavations, the collection of material is now static. Attention is focused on research.Any further acquisition would have to comply with the relevant section and points in the revised Code of Ethics adopted by the Museums Association (UK) and published in 2008.This is the sort of responsible attitude one would dearly like to see more of among collectors of and dealers in portable antiquities in future.
Over on her blog, Kimberly Alderman discusses the SAFE poll about whether museums should disclose their acquisitions policies and says that what she calls "private museums" should not be so constrained (as she sees it as some kind of infringement of "personal rights" or something like that here ). She seems to see this however only as something that could be imposed by "regulation" rather than social pressure. I think it would be a welcome development if a much tighter system of ethics was imposed on collecting from below, from among collectors themselves emulating the more responsible among their number and not allowing themselves to be in any way inferior to public institutions.