Open Source is definitely reaching the 2.0 state and becoming a real alternative to commercial software. However, most of all it proposes value to take "Social Networking" to the NGOs and non-profits who work tirelessly to make changes in their respective societies.
Latest is Kaltura a video platform and DimDim a web-meeting platform. These are just two of probably hundreds such software platforms making the news. As a specialist in collaboration technology my personal favourite has been Drupal and civiCRM.
My thoughts immediately go to the small non-profits driven by energetic, passionate and skilled idealists -- always short on funds and striving to make the kroner or rupee go as far as possible. Looking back at the 80s, I see how user-centered design became possible when Microsoft, Lotus and Borland let-loose the power of the PC with development tools and software architectures. This ultimately led to mass adoption of computing in the workplace. I sense a wave of citizen-centered design approaching and I wonder how governments and bureacracy will react. More on this later...
I suspect Kaltura will be challenging the likes of YouTube and Google Video - not directly - but in allowing for the development of solutions without the hassle of those "pesky ads". And DimDim is taking the battle to Microsoft, Google and Cisco (Webex). On the other hand, these could also be partners... it is difficult to say in this new era of Darwinism; those who adapt will survive. The trick is in "How to adapt".