Big agencies have always been faulted for moving too slowly, especially when it comes to embracing fundamental changes such as the advent of TV in the 1950s and digital in modern times.
We can all learn from small agencies, including ones outside the U.S., because they move more nimbly and adapt with the times much more easily.
I recommend this AdAge.com article by Andy Gould, who shares his small agency experience embracing digital over the past ten years. There is a lot of wisdom here.
Big agencies are not bad; they have a lot of benefits. They are battleships, however, with much to learn from the PT Boats.