WWW 2009 Refereed Track: Social Networks and Web 2.0 Track Chairs: Lada Adamic (University of Michigan, USA) Vladimir Soroka (IBM Research, Israel) Program Committee: Mark Ackerman (University of Michigan, USA) Helen Ashman (University of South Australia, Australia) Rafae Bhatti (IBM Almaden, USA) Athman Bouguettaya (Virginia Tech, USA) Ciro Cattuto (ISI Foundation, Italy) Nosh Contractor (Northwestern University, USA) Scott Counts (Microsoft Research, USA) Jon Crowcroft (University of Cambridge, UK) Nathan Eagle (Santa Fe Institute, USA) Shel Finkelstein (SAP Labs, USA) Danyel Fisher (Microsoft, USA) Jill Freyne (UCD, Dublin, Ireland) Lise Getoor (University of Maryland, USA) Werner Geyer (IBM Research, USA) C. Lee Giles (Pennsylvania State University, USA) Natalie Glance (Google, USA) Scott Golder (Cornell, USA) Ido Guy (IBM Research, Israel) Susan Herring (Indiana University, USA) Matthew Hurst (Microsoft Live Labs, USA) Michal Jacovi (IBM Research, Israel) Matthias Jarke (RWTH Aachen, Germany) Akshay Java (University of Maryland-Baltimore County, USA) Ajita John (Avaya Labs, USA) Lalana Kagal (MIT, USA) David Kempe (University of Southern California, USA) Pranam Kollari (Yahoo! Applied Research, USA) Gueorgi Kossinets (Cornell University, USA) Tessa Lau (IBM Research, USA) Kristina Lerman (USC, ISI, USA) Gili Leshed (Cornell University, USA) Jure Leskovec (Cornell University) David Liben-Nowell (Carleton College, USA) Vittorio Loretto (University of Rome, Italy) Program Committee (continued): Cameron Marlow (Facebook, USA) Yutaka Matsuo (National Institute of AIST, Japan) Massimo Mecella (University of Rome “La Sapienza,” Italy) Filippo Menczer (Indiana University, USA) Bijan Parsia (University of Manchester, UK) Adam Perer (University of Maryland, USA) Anabel Quan Haase (University of Western Ontario, Canada) Sheizaf Rafaeli (Haifa University, Israel) Gilad Ravid (Ben-Gurion University, Israel) John Riedl (University of Minnesota, USA) Rahul Sami (University of Michigan, USA) Barry Smyth (University College, Dublin, Ireland) Eyal Sonsino (Google, Israel) Ellen Spertus (Google Inc., USA) Anna Cinzia Squicciarini (Purdue University, USA) Kien-Lee Tan (National University of Singapore, Singapore) Milan Vojnovic (Microsoft Research, UK) Chris Volinsky (AT&T Labs–Research, USA) Dennis Wilkinson (HP Labs, USA) Volker Wulf (Fraunhofer, Germany) Haizheng Zhang (Microsoft Live, USA) Jun Zhang (Pitney Bowes, USA) Aoying Zhou (Fudan University, China) .