Okay I guess the bottom line is all folders can open if the unexpected happens, as stated above the sebenza has been along a very long time and is not a grail knife if this was a unique issue.
Since mine opened in my pocket the possibility of a knife opening has been something I consider when purchasing a knife. I have to say that the Spyderco Manix 2 (S90V Version) is now my perfect EDC. It has a very strong detent that will pull the tip of the knife closed from over 1/2" deployment out of the handle. And it has no thumbstuds or thumb disk to get snagged and pull the blade open.
If you are really concerned about accidental openings, which is something I am concerned about, then I would strongly recommend that you give the S90V Manix 2 a close look as a Sebenza alternative.