google:
  id: 1
  user: marc
  link_id: 1
  direction: 1

yahoo:
  id: 2
  user: daniel
  link_id: 2
  direction: 1

reddit1:
  id: 3
  user: marc
  link_id: 3
  direction: 1

reddit2:
  id: 4
  user: fred
  link_id: 3
  direction: 1