It depends on the countries that have high pc and warez knowledge..
India, usa and china are just really big countries, so naturally there will be more visitors.
Chinese people are more into social networking, and also they are not that wealthy, so not everybody has a computer.
Indians are money seeking and they don't like to spend, and thats why ad companies and filehosts don't pay for the indian traffic.
People from usa are easy to convince so they buy stuff easily if the ad is good. Countries with good pc and warez knowledge are russia, serbia, greece and germany.