“Although the total number of electrons in the memory does not change as the stored data changes,” Dr. Kubiatowicz said, "the trapped ones have a higher energy than the untrapped ones. A conservative estimate of the difference would be 10–15 joules per bit."
So there you have it. Weightless ebooks are a myth, and each ebook that you load for a student is one more brick that will eventually cause, well, nothing. it would likely take a few billion books before you could even measure the change and even then you could equalize the weight by peeling one of the safety labels off the case.
I followed up with the professor, and he didn't think it would get this much attention. This was all based on some back of the envelope kind of estimates, and while he trusts the numbers he didn't do any extensive research and testing before answering the question from the NYTimes. But it sound like he might do a paper on this. If and when it's available I'll post a link.
image by caryatidxx