In particular, Amazon will not allow sites using the API to link to the book on any other on-line retailer except Amazon, but Goodreader provides links to titles on multiple retailers. Also, Amazon will not allow content from its API to be used in mobile sites or applications. Goodreads will switch to paying to license data from Ingram, and will also use information from the Library of Congress and other sources.
The change is causing concern amid a number of Goodreads users that data about some of their books might be lost in the shuffle, but Goodreads is hastening to reassure users that their data is “100% safe” and it is taking measures to safeguard any books that are in danger of losing their information.
The moral of the story is to be careful about relying too much on “free” services provided by a company out to make a profit. You never know when their needs will come into conflict with your own.