The message included Mr. Bezos’s mea culpa from July. “This is an apology for the way we previously handled illegally sold copies of ‘1984’ and other novels on Kindle,” Mr. Bezos said. He went on to describe Amazon’s actions as “stupid, thoughtless and painfully out of line with our principles.”

Image Jeffrey P. Bezos, Amazons chief, apologized to Kindle customers. Credit... Mario Tama/Getty Images

The troubles began when the novels were added to the Kindle’s online store by an outside company that did not have rights to them. After the rights holder alerted Amazon, it removed the unauthorized versions from its systems and from customers’ devices, distributing refunds.

But neither the refunds nor the subsequent apology were enough for some critics, who said the incident underscored the depth of the restrictions built into the Kindle. Digital books for the Kindle are sold with so-called digital rights management software, which allows Amazon to maintain strict control over the copies of electronic books on its reader and prevents other companies from selling books for the device.

Consumer advocates and civil libertarians say the system could allow courts or governments to force Amazon to recall, and in essence censor, books that they deem politically dangerous or embarrassing.

The critics say the problem arises not just with Amazon, but also with other services offered online, like Google’s planned digital library or streaming music and video sites, that replace tangible products like books, CDs or DVDs.