Hi,
I just came across this page on the net and it has got some useful info regarding who the real people behind Linux are. How is developing it, how many developers are involved, top developers and their individual contributions, total lines of code, companies that help them etc etc.Thanks...
http://www.linuxfoundation.org/publications/linuxkerneldevelopment.php
Any other reliable document that you are aware of citing the exact/approximate no. of developers worldwide?