A popular and useful feature of Amazon's Kindle is that highlights and notes that you put into one of your eBooks are stored on Amazon's servers and automatically applied to other copies of the eBook that you own. So, for example, you can put highlights into a copy of an eBook on your Kindle 2. If you download and open the same eBook using Kindle software on your PC, the highlights will be there.
However, according to MSNBC.com, Amazon is now aggregating highlights from its customers into a feature that it calls "Popular Highlights". If at least three people highlight the same passage, those highlights are made available to any Kindle user who wants them. The names of the people who made the highlights aren't displayed, but from a privacy point of view, that doesn't matter; Amazon is keeping track of its customers' highlights and is revealing that information without their consent.
When readers put notes and highlights into a printed book, they usually do so with the expectation that those annotations will remain private. Amazon has decided that it can do whatever it wants with your highlights, as long as it anonymizes them. Some Kindle users have reported that they've tried to opt out of the program and were told that they would lose the ability to backup their annotations on Amazon's servers and to share annotations between readers if they did so. In short, using Amazon's Whispernet service to store your annotations is tantamount to giving Amazon permission to use them as it sees fit.
Given the reaction to Facebook's recent privacy moves and Amazon's previous missteps (for example, deleting without warning eBooks that consumers had already purchased because of a copyright ownership question,) you'd think that it would have thought Popular Highlights through with a bit more care before implementing it. In any event, look for yet another "mea culpa" letter from Jeff Bezos real soon now.