U.S. is quiet cause law enforcement uses these things to gather intel. Patriot act allows information gathering. Drug use can be considered act of terrorism (its a stretch but possible) since drug money often funds counter-cultuture and extremist views.
I guarantee many of us are already on lists somewhere.....any admission of use, traffiking or manufacture makes your user name go on a list then user name is crossed checked with other boards and places where your ip address is obtainable (many use the same user name every where they go) to deduce your true identity. All this goes int database with your location and suspicious stuff you posted.
Even if this board does not comply with Homeland security or DEA/FTA because it is in AU, other boards where you use same user name might. Ip address get's checked on WHOIS and domestic ISP must comply with homeland security.
You have no privacy in USA so writing things down is risky.