In SEO terms, a big deal is made of the practice of building links. This is because the major search engines view each link as being an indication of the quality of your page.
Call to action buttons are something that are sometimes taken for granted. However, when they are used well can be huge money makers. On an interview I did once I was asked about Call-to-Action buttons. What my thoughts were and what I take into consideration when creating them. Up until that point I didn't really understand what he meant. At that time I put as much thought into the call to actions as it took to make a button pretty and visually appealing. If I am not mistaken I told him some gibberish about color. Since then I have done a lot more reading and have gained a much better understanding for what he was asking me.