From author Nathan Bransford’s blog about the imperfections but usefulness of social media:
3) There are benefits to using social media beyond sales
If you’re only using social media to sell books you are absolutely using it wrong.
Yes, it can sell books. But the sales benefits are far down on the list of benefits that you will accrue using social media the right way.
More likely: You are making friends, you are learning about what else is out there, you are exchanging knowledge, you are discovering, you are communicating, and opportunities will come your way as a result.