It's a step in the right direction and it's a signal. If Facebook can afford to do this then other companies can afford to do it too.
Positions which do not provide value > than the minimum wage will be eliminated, either because the roll they fulfill can be automated at that price point or its no longer worth while to the company.
There are, of course, marginal roles and not-very-profitable businesses where the value of an employee is pretty close to the minimum wage.
It in no way means all or most other companies can afford to do so.