When the rock histories of the 2000s are written, at least one long chapter will have to be devoted to the explosion of the concept of the rock band not as a small, discrete unit with relatively stable personnel, but as an amorphous, free-floating collective that could at times expand to include dozens of people. Canada's Broken Social Scene and the pan-European ensemble the Envelopes are perhaps the best-known examples, but I'm from Barcelona -- whose members actually hail from Jönköping, Sweden -- may have them beat in terms of sheer scale: 29 bandmates performed on I'm from...