You can use referral trackers anywhere that you post a link back to a HubPages Hub or Video. Using referral trackers on links to your content will ensure that you get credit if someone who clicks that link signs up for HubPages. Using referral trackers on links to content by other HubPages authors will provide you a 10% credit on any earnings generated from someone who clicks that link, including if they sign up. The author gets their standard 40%, so it is beneficial to both you and the author.
If anyone wants to share my Hubs using referral trackers, please feel free to do so. :-)