Duncan wrote: If that's the case, then why would someone register the company in Cambodia ? Why not, lets say Nigeria.

you can register your company anywhere in the world (provided you have got the paperwork required for that country) the main problem is tax, MNC usually have to pay higher tax (unless that country have low tax rate, ask apple, google etc)

For online companies it's common to register in a different country, however it's depends on how easily you can manage bureaucratic issues and taxes from abroad, also the legal framework of a certain country needs to be taken into consideration as it can create problems. For example double taxation could be an issue if you operate a business in a country while it is registered in another. So you need to consider the various aspects of your business. An online casino for example has less connection to a certain area (and can dodge taxes more effectively) than an online supermarket which needs warehouses and couriers. Often online casinos are registered in whatever jurisdiction is more welcoming to them (less taxes and easy licences) for example Vanuatu islands, even if it's target clients are anywhere in the world.
So when you register an online business abroad you have to evaluate the advantage of operating from tax heavens and the legal limits which often they are subject to (problems with banking, black lists, lack of accreditation, PayPal not accepted etc.) From the countries in which you actually wish to find your clients. Many more things can be said on the topic but it's a quite complex issue.