There has been an attempt to solve a long-standing mathematical problem in a massively collaborative way. It is called the Polymath1 Project and looks to provide a new proof of the density Hales-Jewett (DHJ) theorem. Apparently, after about 7 weeks, it looks like they have done it. Details are here. I’ll leave it to you to wonder about the potential of all of this.
In a related note, David Pogue laments the lack of attribution to the original authors of Internet jokes. Believe it or not, this raises key issues of relevance to collaborative science.