Selling books

I was talking to a rare books seller recently about the changing nature of his business. The larger part of his sales are now made on the web, through such services as ABEBooks, Alibris, and for some things, eBay.
This raises an interesting inventory issue. In his walkin-in store, books are organized to support a meaningful human browse experience. And browsing humans move books around.
To support his online business, books are better organized for rapid retrieval, ordered by some simple key. They should be predictably available so having them moved around is not good.
His business is co-evolving with the web, and posing interesting questions about priority and organization as it changes.