Actually the idea in the article that it was to keep the USSR generals and stuff from doing stupid things like launching first attacks because it would make sure they could always strike back was quite interesting.
In other words, the whole point of a doomsday weapon was not lost because they kept it a secret.
I still think, however, that it's not a practical deterrent for reasons that movie makes all too obvious.
The Wright Bothers weren't the first to fly. They were just the first not to crash.