I'm with toujour on the precept and karma aspects of pot and the other issues. I might have very well financed several small south american countries when I was younger, and I only have one tat, the result of mixing boot camp, alchohol and a day off.
I think what we really have to look at here is what your intent is in using drugs, piercing, tats etc. What are you trying to gain by these things, and is it something that you would be gaining through greater effort rather than taking the short cut?
The clarity of thought that seems to come with pot use is short lived actually, and if you live long enough you begin to notice a "glass ceiling" of sorts in your meditations. Almost as if pot takes you into another room well decorated with thangkas, Icons, starlight, and all that, but you begin to notice that your surrounding begin to look plastic, and somewhat two dimensional after all.
Again, I find it helpful to focus on what my intent is in any action I decide upon and ask myself the tough question, "Why am I doing this?"
Peace