From my (very limited) perspective, this seems to be mostly publicly clarifying the roles they were already effectively serving in their ad hoc division of labor for a while.
Larry has been the most involved in the technology details, Sergey has been the most involved in the blue-sky new projects, and Eric has been the most involved in the interaction between Google and other entities (as well as very high level direction.)
Larry has been the most involved in the technology details, Sergey has been the most involved in the blue-sky new projects, and Eric has been the most involved in the interaction between Google and other entities (as well as very high level direction.)