For instance:
1. Consider a journalist who doing an investigative story on amazon's warehouse working conditions. The journalist has been given some internal documents used by amazon and happens to search for one of these documents. Amazon could detect that someone has this file and learn of the investigation.
2. Or someone has pirate a movie and searches for the file on their harddrive. Given certain search strings it should be possible for amazon to detect that this purpose engages in piracy. What is to prevent amazon from reporting this information to "The Authorities".
I hope someone develops an Ubuntu fork that doesn't have spyware (spyfree-ubuntu?).