Sandi, The club is actually called "Detachers Anonymous".
Going dark for me was because W was involved in an affair. I don't feel comfortable with divorce, so it was the appropriate response for me. I actually asked W flat out to respect our children and our marriage by ending the affair. She didn't, so I responded. It actually was a last resort for me. And if you look at different threads - Silva, Tawnya, Pearl - many of them have benefited by going dark. Tawyna was detached - and only went dark when her H moved out.
While I don't feel that divorce is right - I can make a stand that our communication will be limited to bare essentials while she is engaged in an affair. I pledged to myself a month of going dark, and it has been amazing. My W does live in a separate apartment.
It has served three purposes: 1. To give W a feeling and knowledge of what life would be like without me - because if she proceeds with divorce, our relationship ends completely. I will notify her of our kid's needs and any other appropriate information, but other than that, she will cease to exist to me.
2. To help me regain my sanity - W is up and down alot, and I tended to pogo with her. This separation, although hard, has really allowed me to actually detach. It has also gotten me to a point where I don't really think about what W is doing or where she is - it has been huge for me mentally.
3. Completely wrestled control from W. I wouldn't say that it has given me control, but she has controlled for so long, that it is driving her crazy now!
My situation is not the same as everyone else's obviously. Also, I think "going dim" is the same as detaching - at least in my mind.