There is a substantial amount of spam and NSFW posts on the All page coming through already. Most NSFW posts aren’t being tagged as such and are coming right through. I am not sure how this can be weathered but we need something in place fairly soon, I feel like we are days away from rivers of bad stuff, especially via some of the federated instances.
EDIT: I personally don’t care much about the NSFW aspect, more in the lines of what a newcomer will be seeing when they get to the main page. 99% of the newcomers don’t know / care about federation and have no idea how to turn that off. Liability for the server owner is also an element of consideration.
Several people here are saying that the bulk of it is coming from lemmynsfw. If so then it may well be best to defederate in the short term to buy time for a better solution (like marking everything from there NSFW automatically, either by a lemmy enhancement on their end or a kbin enhancement here)