In the lifestyle of BDSM, there is a phrase 'oft used: "Safe, Sane, and Consentual"
It's a great idea, a worthy goal, but it has a couple of problems:
Who decides what is Safe? And for that matter, who decides what is Sane? If the parties involved are deciding what is safe and sane, then why bother with those two words? If someone else has to decide if it is safe or sane, then we have to find a way to clearly define those meanings. And that turns out to be pretty darn hard. Even the guy who coined the phrase says he regrets it. What is safe for an experienced Dom/sub may very well NOT be safe for the newcommers. Sanity is even harder: The DSM 4 is a heavy read.
Consentual is much easier: If all parties agree, and do not object or use thier safe word(s) then, clearly, it was consentual. This is the one thing that we had best stick to and make sure we are following. yeah, try to be safe, try to be sane, but for darn sure be consentual.