The wording on license agreements with eBook readers and eBooks themselves is a bit muddled. On one extreme, you can't loan eBooks or eBook devices to others. This might irritate customers but this is a bigger concern for institutions like libraries. (Here's one interpretation for example.)
Barnes & Noble's Nook and Amazon's Kindle have book loaning book options (Nook|Kindle), one more recent than the other.
The Good: The companies thought about it.
The Bad: The solutions seem to be a step backwards. My analogy is that you have a horse that can run 30 mph. The companies, however, don't want the horse running at 30 mph so they add weights to it, so that it runs at 3 mph. My problem with the book loaning options is that instead of embracing the advantage of the electronic format (the fact that it's digital, easily copyable, etc.), it's crippling it. And remember my last post on how the eBook market revolves around the US and the UK? Here's the quote from the Kindle article linked above:
"Lending can only be initiated by U.S. customers, and recipients won't have access to certain books in certain countries."