Have you noticed how every podcast ends with an ask for a review on iTunes? It is a call to action. If podcast does not ask for reviews, they will get none. That equals less listeners.
Ever noticed that the tweets that ask for retweet get more retweets than tweets without a retweet request? This is especially true when using Twitter on a smartphone. It is a stream of information and you consume it with micro interactions, few minutes at a time. That is why you have to ask for retweets if you have something interesting to share.
Googling “anatomy of a call to action” will give you number of good blog posts and examples. Simplest example is a landing page for upcoming product launch. The purpose of the landing page is to collect emails from visitors who are interested. The signup button on the page has the biggest visual impact on the screen, making sure that it is the first thing your eyes focuses on. If you do not do it, your landing page does not convert visitors. It means you have built a web site which does not fulfill the purpose. It means you have wasted time. Make sure you have a call to action.
This is a good lesson for everybody who is spending their time at the outskirts of the web, wondering if they should promote their projects and products. Do not bet on viral effect, it’s the exception of the rule. The Internet does not give you anything unless you specifically ask for it.
It would be little self-serving to ask to share this blog post to your friends… :)