Well, my book sales supposedly total about 50,000 for the two books and they are not the best sellers on Amazon so I would imagine there are over 200,000 certification books in print and surely a large fraction of those have led to passing the exam. The Sun JDK downloads are in the millions so I would guess over 100,000 SCJP. In the consulting biz we would call that a SWAG! Scientific Wild Ass Guess Bill
So if their are 300,000 mcse's in the usa, I am thinking there are <120,000 sun certified java programmers. for Sun certified developers I am thinking less then 20% of the programmers, so that is 24,000. Look at the number of messages at the developer test section in comparision to the programmer certification section.