Do what's right and report as much of whatever violates their TOS as you can. You're not going to be able to report everything, especially since Facebook's lack of enforcing their own TOS has encouraged Facebook users to increasingly misuse Facebook, and since reporting content that violates Facebook's TOS can become overwhelming. There even have been a few instances of late in which I've reported stuff that Facebook has frustratingly not removed, and instances in which I've reported stuff that I did not actually expect Facebook to remove because of how inconsistently they enforce their own TOS.