Social media systems allow users to share resources with the people connected to them. In order to handle the exponential growth of the content in these systems and of the amount of users that populate them, recommender systems have been introduced. As social media systems with different purposes arose, also different types of social recommender systems were developed in order to filter the specific information that each domain handles. A form of social media, known as social bookmarking system, allows to share bookmarks in a social network. A user adds as a friend or follows another user and receives updates on the bookmarks added by that user. In this paper, we present an analysis of the state-of-the-art on user recommendation in social environments and of the structure of a social bookmarking system, in order to derive design guidelines and an architecture of a friend recommender system in the social bookmarking domain. This study can be useful for future research, by highlighting the aspects that characterize this domain and the features that this type of recommender system has to offer.