In Twitter, a retweet happens when a user copies another user's tweet and indicates that the content is originally from someone else, and is a common way to share information. This paper explores user’s perceptions of the way social capital influences retweet practices. We discuss how Twitter users perceive values and how they create benefits for the social network and themselves from three points of view: referrals, information access and timing. We do so through a qualitative analysis of questionnaires answered by Twitter users and four quantitative case studies of retweets. We analyze users' motivations, map the spread of retweets and their content, and discuss how referrals, information access and timing can play important roles in what and how users will retweet. Our findings lead to the conclusion that users seek individual benefits but the competition for social capital allows for collective benefits to emerge.