I think facebook is trying to be a country NOT a company. Therein lies its huge valuation.
1. A country with over 800 Million citizens that are all over the world.
2. A country which is rolling out its own passport called verified IDs.
3. A country with its own currency called Facebook credits.
4. A country which has citizens (users) who dont pay any tax to access any of its services or infrastructure.
5. A country where every corporation (Zynga, etc.) that wants to sell to the citizens who buy virtual goods pay a flat 30% tax on every purchase by a user – so yes the user indirectly pays.
6. A country whose benevolent dictator wants its citizens to know its social mission.
7. A country is very business friendly and is increasingly becoming more useful to them.
8. A country with privacy issues with its users to deal with.