i will open a new blog, (for my friends, they want to share what they have) where you will be able to share reviews of art, music, paintings, etc. it wont contain any illegal download link, there will be just reviews. but it could contain references to drug use like: "while i was high i was reading these words" or "you can fly in the sky while hearing this song" could it have adsense?
as long as you are not indulged in any illegal activity or you post copyright protected content you are safe. All the content you post on your website must be urs. as long as u follow adsense guideline , you are safe.
The Adsense TOS state that you are not endorse porno, gambling, drugs - if you adhere to that you should be perfectly fine. My interpretation goes like this: as long as there is no direct invitation to do the nasty it´okay. Still, it keeps feeling like a thin line.... ;-)
And no link to the nasty either, if on your forum you have outgoing links to content violating adsense rules, then that counts as your site violating adsense rules. A simple link for adsense is same as having the content on your page..