“Web 2.0” is the mantra enthusiastically repeated in the past few years on anything concerning the production of culture, dialogue and online communication. Even science is changing, along with the processes involving the communication, collaboration and cooperation created through the web, yet rooted in some of its historical features of openness. For this issue, JCOM has asked some experts on the most recent changes in science to analyse the potential and the contradictions lying in online collaborative science. The new open science feeds on the opportunity to freely contribute to knowledge production, sharing not only data, but also software and hardware. But it is open also to the outside, where citizens use Web 2.0 instruments to discuss about science in a horizontal way.