When a product is set to not active it completely vanishes. This means any any inbound links to the product page land on a disappointing “this page no longer available” type message.
I think it would be great to have a way to discontinue a product without completely killing the item page. This way it doesn’t clutter up the site’s search results, category pages, etc, but direct links to the product page would still result in seeing *something*, perhaps with a stock status of “This product has been discontinued” rather than “Out of stock”.
Currently the “indexed” field partially accomplishes this by removing items from search results, but they still show up on category pages and there is no special stock status that appears when an item has indexed=0 set.