This site is chiefly famous for being the victim of a lynch mob earlier this month. While in reality Lendink was simply one of many legitimate sites that worked with B&N and Amazon to help readers lend each other ebooks, a few weeks back a bunch of ill-informed authors misinterpreted and misunderstood the content and functions of Lendink and jumped to the erroneous conclusion that the site was committing piracy.
I've heard that some 500 authors sent threatening emails and left demands on Lendink's Facebook page in a 3 day period, but clearly the torrent of abuse wasn't enough to keep Dale down forever.
Have you bought ebooks in the Nook or Kindle Stores? Lendink is a site where you might be able to lend the ebook to another Nook or Kindle owner. It's platform specific (Nook cannot lend to Kindle), and the ebooks can only be lent once for a limit of 14 days. If you find you cannot lend an ebook, that's because this feature is only enabled at the permission of the book's author or publisher.