Twitter is a micro-blogging social network service which allows users to share not-so-important things in their life by answering a simple question: "What are you doing?" Answers to this question are organized in a short messages called Tweets, length is limited to 140 characters. The good thing about Twitter, there is no "noise" created by boring people since "friendships" are not mutual - you can "follow" interesting people while they don't have to follow you. In February 2009, Twitter had a monthly growth (of users) of over 1300 percent - several times more than Facebook. Twitter made huge success from the mobile device users (in 2009 there was 735,000 unique mobile visitors).