Postprint versione of the paper: M. Lazzari, “An experiment on the weakness of reputation algorithms used in professional social networks: the case of Naymz”, Proc. of the IADIS International Conference e-Society 2010, Porto, Portugal, March 18-21, 2010, pp. 519-522 © Permission to publish granted by IADIS, http://www.iadis.org AN EXPERIMENT ON THE WEAKNESS OF REPUTATION ALGORITHMS USED IN PROFESSIONAL SOCIAL NETWORKS: THE CASE OF NAYMZ Marco Lazzari Faculty of Educational Studies University of Bergamo Piazzale Sant’Agostino 2 I-24129 Bergamo ITALY ABSTRACT This paper is part of an ongoing research on web reputation, and presents an evaluation of the method used by the professional social network site Naymz to assess the online reputation of its members. By creating six ad-hoc professional communities with different profiles of users and network topologies, it was found that the highest level of online reputation can be easily achieved by engaging a small social group of nine persons or less who connect with each other, providing positive feedbacks and reciprocal endorsements. KEYWORDS Social networks, professional networks, online reputation, web reputation, Naymz. 1. INTRODUCTION The sudden world-wide spread of social networks has transformed them into a rich source of personal information about their members. Personal profiles from social networks are nowadays commonly used by companies looking for new partnerships or employees or by universities selecting freshman applicants (Williams and Lounsbury Morrow, 2008). Therefore, whilst structural properties of social networks have been broadly investigated (Knoke and Kuklinski, 1982; Wassermann and Faust, 1994; Scott, 2000; Knoke and Yang, 2008), the dual problem of building and assessing the web reputation is assuming ever more importance, and has been receiving growing attention by scholars (Goldbeck and Hendler, 2004; Jøsang, A. et al, 2007). In this paper, we deal with it with reference to the professional networks domain. Professional networks, such as LinkedIn, Xing, Naymz, are web communities devoted to interactions and connections of a formal business nature, rather than informal social exchanges, which is the case of social networks such as Facebook or Netlog, which are exploited by their users for fun, recreation, pleasure, discussion or for organizing and coordinating groups and events. Professionals can exploit professional networks to connect to current or former colleagues, establish new partnerships, communicate effectively and discover new professional opportunities. Basic services provided by professional networking platforms consist in functions to describe the member’s profile (personal data, education, professional history, professional and personal web resources) and to connect to other members for building personal small worlds (Milgram, 1967; Travers and Milgram, 1969; Schnettler, 2009). These networks often encourage users to endorse other members, so that the online reputation of a member, fundamentally based upon his/her own profile, can be enforced by the judgment that contacts express through the endorsement. The professional network Naymz sets itself apart from competitors, because it provides an online algorithm to evaluate the reputation of its members: each time a member establishes a new connection, he/she is asked if he thinks that his new contact is honest, if he would recommend him for jobs, if he would like to be worked with, if he wants to be considered as a reference for the new contact and if he wants to endorse him. These answers increment a RepScore, that is the reputation score of the member, on the ground