-- it's seems blatantly personal decision and potentially a dangerous one.

I agree wholeheartedly. Especially since I believe that the big guy who abducted Nick from the crime scene was not Walter Gordon but probably Gordon's accomplice. And we don't know yet if Nick told anyone about Kelly Gordon being released and showing up at not only a crime scene but at the lab. Nick and Grissom each know about one possible accomplice so I can only imagine the fall out when they finally learn about both of them. I can see them getting upset with each other for doing the exact same thing. :)

Not telling Nick about the second voice on the tape raises a few possibilities. Is Grissom secretly watching over Nick (something I wouldn't mind)? He has to know that Nick might need some kind of protection if he's going to be kept in the dark. Does Grissom already suspect someone (like the cop with Nick that night) and is watching them? Whatever it is I think you're right: the decision seems personal even if it's a little wrongheaded. Loves like that.

anyway, I m ranting again.

Not. A problem. :)