How many companies have certified under ISO 27001? You can find the answer here. So, under 7300 as of mid-August 2011.
Now, in another report from April 2008, there were 4500 certificates. With the distribution: Japan (2550); UK (370);India (430); Taiwan (175); China(110); Germany (90); and then a group of countries (Hungary, Italy, USA, & Korea) at 60.
The distribution remained pretty much the same, with Japan holding more than half of world-wide certifications. Japanese are mad about productivity, so by adopting a standard they accept a set of rules that work.