From our perspective, Web 2.0 is in essence "collaboration in an untrusted environment". The Web 2.0 environment allows many individuals to separately manage their own territory on a shared server (e.g. personalization), while sharing a multitude of content formats. This creates a lot of opportunities for malicious individuals to extend their reach beyond their personal space on the server and distribute malicious content using a multitude of potentially vulnerable formats. All of this is of course achieved through an interface with rapidly growing complexity (AJAX based GUI using cool widgets and mashups). This openness and complex mix of technologies is what makes securing Web 2.0 services such a big challenge.