I claim that anyone who buys books on the Kindle is in fact renting them, just for an unspecified duration that Amazon gets to choose after the fact. Amazon has

I claim that anyone who buys books on the Kindle is in fact renting them, just for an unspecified duration that Amazon gets to choose after the fact. Amazon has already demonstrated that they are capable of remotely deleting books on people's devices, so your rental will last as long as it's in Amazon's financial interest for it to. That will probably be as long as Amazon exists as a company, but who knows.