I finished up a paper today so it is time to start a new one. In doing preliminary research for the new paper, I stumbled upon this roundtable on the Diversification Discount. It is excellent! Very interesting. And yes it is two years old, but still well worth your time!
SSRN-Research Roundtable Discussion: The Diversification Discount by Belen Villalonga: " Villalonga, Belen, 'Research Roundtable Discussion: The Diversification Discount' (April 24, 2003). http://ssrn.com/abstract=402220