Tagging sites allow users to post information and organize it with tags for future retrieval and to optionally share their entries with others or keep them private. Some tagging sites also allow users to add personal reviews to their entries. Sites that offer publicly available information that includes user-generated reviews are designed to function as social recommendation systems. However, since sharing is voluntary and reviews are discretionary and laborious to produce, it is not clear whether a site with these optional features can function as a social recommendation system. Using activity data from a site with these characteristics (11870.com), we test whether contributors use it as a social recommendation system. We find that the prevalent user profile is that of a public contributor, for whom the proportion of entries annotated with reviews is 68%. Almost 40% of the public contributor base, particularly newer users of the site, provides reviews for all of their entries. Our results indicate that this tagging site is increasingly viewed as a social recommendation system despite the discretional nature of sharing resources and adding reviews. An important implication of these findings is that optional features do not undermine the ability of a tagging site to function as a social recommendation system.