Up until this decision there was somewhat of an excuse for companies like Facebook, Apple, Microsoft, etc. since there was this Safe Harbor agreement that basically just stated that 'everything is fine.' But now, Safe Harbor is dead. And making another Safe Harbor agreement will probably fail.
This is not something that can be resolved by Facebook with an update to the Terms of Service. Probably because it would be anyway invalid according to EU law but also because they are bound by gag orders from secret services that explicitly forbid them to state what exactly they're doing to the data. At this point, it is completely unclear what will happen and what Facebook and other US companies will do.
One possibility is to store data in the EU, effectively hiding it from US mass surveillance. However, there are most likely significant costs involved with such an approach.
We need to wait and see. These are interesting times.