You can get a bonus for a redirect from a post on a personal page (the Wall, the News feed, etc.); if you reach a new level, complete a task, or exchange a collection, you can post a note of that in your feed. Should any of your friends open this announcement, each will be entitled to a bonus in the game. You can earn up to 30 bonuses per day in this manner. The bonus is valid for 24 hours once the announcement is posted. You can only receive the bonus from the announcement of the person who is your friend.
It is often a good way to find a missing element for some collection you haven’t completed.