I live in India. I need to start a social networking site here for the indian users as well as spread it to users abroad in USA, Europe, Australia. As of now, I start as a 1-man startup. I need to confirm whether I need to incorporate just here in India alone & let my website be used by people all over the world or do I need to incorporate separately for each country where I wish my website to be used ?
I also would like to accept payments from advertisers all over the world.
The dominant issue for a social networking site is user privacy. Each major jurisdiction has laws governing such (though to call US privacy 'laws' is giving them more credence than creed). For example, Europe has Data Protection Directive where any private information of an EU citizen is not permitted to travel beyond its borders unless the matching jurisdiction has equivalent privacy laws (eg Australia/NZ). China also recently released Draft provisions. By incorporating in India, you are bound by domestic laws (apologies I'm not familiar with privacy provisions there) and any international treaties (or lack thereof).
The other international aspect is permission to distribute the user-generated content (aka walled gardens). What other websites have tried to do is to convince users to be bound by Terms of Service including home jurisdiction (see Craiglist in asking for non-exclusive, irrevocable copyright over all content). This is an open question as international law is that as a service, it is performed in the country where the service is deemed to be performed. Hence the french govt could force google to follow french laws for its citizens.
Accepting monies a matter of signing up to a payment gateway though I'd suggest rethinking the advertising model given the sophistication of US offerings.