An H-1B only requires a Labor Condition Application (LCA) which is basically an agreement to pay the prevailing wage and an assertion that there's not an ongoing labor dispute (strike, lockout) ongoing at the proposed location of hire.
However, from what I understood, it only applies employers who have been designated H-1B dependent (something like 15% of their workforce is H-1B) or something like that, or were identified abusers of the program. And even then, there is a salary limit, i.e. if you are paying over $X (which I am assuming facebook is), even if you're workforce is a high enough proportion H-1B you would be dependent, you are still exempt.