Besides informal relationships with the authorities, I don't see why they "have" to abide by any local law?
PS: Tunisia has internet transparency laws, so they can't go blocking Facebook (or any other website) at a whim.
I strongly agree with you on the idea that companies and people should only need to obey the laws of the countries they operate in, but you must recognize that this idea is not currently the status quo, is actually fairly radical, and is strongly opposed by a lot of very powerful governments, including the United States.
Kim Dotcom had servers in the US - in fact, nearly their entire server fleet if not entirely was in Virginia, vendors in the US, collected payment for illegal downloads and uploads in the US, in USD. Their primary domain was a .com, which is owned by Verisign, a US company.
This would likely not be the case if you were running on a ccTLD in your own country, hosted in your own country, at least.
If you are in Canada and hire somebody to rob a bank in the US, you have violated American law and can be extradited. This works in reverse too. If you are in the US and hire somebody to rob a bank in Canada, you have violated Canadian law and can be extradited.
>For example, see Kim Dotcom.
Poor example because Megaupload had a US nexus.