If this went hand in hand with digitization efforts (for books that are not copyrighted anymore), at least it would help to spread the knowledge. Something like what Google's been doing. And there are book types that exist in excessive supply. Dated encyclopedias come to mind, but also many others. Anything that's been printed for mass market can take a hit. So for me it really depends on what these supposedly rare books are.
But the voracity and, I can only presume, lack of selection criteria on which books are ingested, is worrying indeed.
But the voracity and, I can only presume, lack of selection criteria on which books are ingested, is worrying indeed.