motorhaven - 4:36 am on Jul 29, 2012 (gmt 0)
Most of my list visitors (depending on which of the several sites I have) are from the US, Canada, western Europe, Australia, New Zealand, Mexico, a spattering of middle-eastern and African countries and a couple of countries in Asia.
99% of my problems originate from China and Asian countries, eastern Europe, Israel, Netherlands, and a couple of South American countries. Also some host farms in Germany/England and a boatload of hosting companies in the USA (none of them in the 4.x.x.x range). Even with problem areas such as Asia/East Europe I take a scalpel rather than butcher knife approach. I've taken a butcher knife approach before and watched Adsense revenue drop as a result.