Originally Posted by Nilotikus
I guess it's the difference between copying a file to another device and moving a file to that device. If you move it to a friend's reader you won't have a copy to read.
But you'll still have the book in your Kobo library account, and probably also on your PC's hard disk. As I said before, the reason that so-called "lending" of ebooks is different to lending a paper book is precisely because you're not simply moving a single copy around, but creating duplicates.