I wasn't planning to be a huge fan of the book lending thing because of too many catches. But I'm still excited because I noticed that some of my ereader books on the B&N web site are already marked as lendable. I really can see this as a cool, workable feature because I have so many books I buy because the price is good right then or whatever but don't plan on reading right away.
For example, I bought K. O. Dahl's Norwegian detective story
The Man in the Window even though I haven't finished the first book yet (which I have in paper) because the e-book price was good. And it turns out that it will be lendable. But I won't be reading it for some time because I'm still finishing Dahl's first book,
The Fourth Man.
Once the feature is available, somebody will be able to borrow the e-book from me.