Authors: What to do about ebook ripped and shared?

So I happened to do a search on my book and discovered that the top results no longer link to my website (or Amazon or Powell's or Alibris or whatever) but instead to a wide variety of file-sharing networks.

Is this normal these days? Do I combat it by doing the same, offering my own free download? Do I contact all the forum managers to remove such posts - or is that a Sisyphean effort? Or do I not try to combat it at all and learn to like it?

Huh!

Thanks for any advice,
Chris