Just an avid reader. Mostly SF/Fantasy, some hobbies, paranormal, urban fantasy and lighter, fluffier things.
Just curious. And curious if Amazon has ever commented on why or why not. Ditto for Google Play, iBooks, Barnes and Noble, et. al.
(It seems weird to me that Google Play — who seemingly indexes entire book for search purposes even without author permission and well beyond usual "look inside" options —would not use that index to check for plagiarism. Or maybe not since have their own notions of what copyright means.)