In contrast, Amazon uses a proprietaryfile format that only allows users to read books they've bought using the Kindle, or Amazon-sanctioned Kindle software.
One main reason: The company had a history of religious devotion to proprietaryfile formats, and took years to release a digital audio player that could handle the ever-popular MP3 format.
In total, the file was made up of 19 million queries made between March 1 and May 31 on AOL's proprietary software, which until last week was available only to paying subscribers.