Gal Granov of Whisky Israel just published a thoughtful post about selling empty whisky bottles on eBay. Empty bottles of sought-after whisky often fetch astonishing prices indeed. The German version of eBay has a very busy whisky section (beause the ‘collectible container’ workaround is not necessary here). A search of finished sales for “Leere Flasche” (empty bottle) usually brings up amazing results, sometimes going into three figures.
Of course you can ask if collectors of empty bottles really are that generous with their money, or if these bottles will show up again a few months later on eBay or other whisky auctions, re-filled with whatever and re-sealed.
I agree with Gal that selling your empty bottle of a rare whisky may supply whisky fakers with new material to work their evil upon. But there is another aspect to be considered. As a seller you obviously get the contact details of the buyer. Now if you manage to sell your empty bottle for an obscene price, you have name and address of somone who could (not necessarily must!) be involved in faking whisky.
It should be possible to prepare empty bottles in a way that they can be identified later, maybe even visible on a picture if you know where to look. The majority of rare whisky bottles is likely to be sold on eBay or a few other auctions/platforms, so it should also be possible to monitor them. Just an idea…