Social network services (SNSs) are now the primary advertising medium in terms of both reach and engagement. For both businesses and the SNS providers, it is crucial to find advertising methods that users perceive to be valuable. In this paper, we provide an empirical evidence for the role of different advertising methods on SNSs (i.e. earned vs. paid) on the subjective evaluation of the relative worth of advertising. In particular, we concentrate on the act of 'friend tagging' - the convention of tagging friends in a thread to a brand post - where users inadvertently engage in targeted and personalized brand advertising. Through survey analysis, we validate that users find earned advertising less irritating and more informative, entertaining, and credible than paid advertising. We further ask if brands can strategically craft their content to boost up friend tagging. Using the data collected from Facebook, we analyze what drives users to engage in friend tagging and find that content characteristics such as media attachments and posting times affect friend tagging frequency. We conclude that friend tagging is a powerful user-initiated solution for matching products with potential target audience.