I'm not aware of a netflix policy whereby a movie will be deleted from its servers once a set number of downloads has been reached.
The time thing was similar I thought, which is why I mentioned it. If you really want to know the answer to this question, call Netflix.
More interesting, at least to me and pertaining to the Harpercollins Library Debacle, is the fact that a good portion of books that are checked out from libraries are not read, perhaps a portion of all of them are, but I expect some taxpayer money to be lost to the aether of unread books if this idea is spread beyond where it currently sits.
An example,
10 people check out a book and read it in its entirety
The next 5 people check out the book then forget about it and the book is deleted from their reader.
11 more people check out the book and read it in its entirety.
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How many book reads have been lost?
5
But the money for those reads has already been transferred to the publishing company, I do hope this is clear, they have been paid by the taxpayer for nothing.
To be fair, this has not yet occurred, as least to my knowledge, But the fact that the idea has been taken as far it has, it does not bode well.