The only time I've seen cursing is when kids or teens are going through the 'loud and obnoxious' phase. I'm still annoyed that parents can't discipline the kids during this phase, and it seems like all my kids go through it once when they're kids and once when they're teens. (Why can't they have the 'unbearable sadness' phase, which is so cute? No, it's always the 'loud and obnoxious' phase.)
In any case, I don't think I've ever seen an adult curse, and outside of the phase, I haven't seen it with my kids and teens, either. Mod issue?