If you are running a vBulletin board, the stopforumspam.com is a must as long as you configure the plugin to prevent some false positives. I would also suggest using BlockScript to prevent registrations from proxy servers.
A lot of legitimate members actually come from China and India I find. So that may not be great advice, but I would definitely agree with the other countries, sir.
As far as profits are concerned, allowing India just isn't worth it. Ad companies pay peanuts for their traffic, their PayPals seem to have extra dumb rules for some reason which reduces the number of potential clients, and most of my chargebacks seem to come from that area. Knowing China, your site is probably already blocked there -.-
When I used to run a network of websites, I used to earn 7% of my monthly earnings from India and China. (6% from India) It's worth it. China is a funny country when it comes to blocking websites, so I wouldn't be surprised if you are actually right with that comment there.