rotorspeed:
You do not need freak conditions and you can have 10 miles of visibility to get into a situation where all outside reference is lost. Flying in the winter in Alaska, in the mountains or over water with an overcast is an eyeopener . There was one accident where a company lost 3 ships on the same glacier on the same day. Fortunately nobody was killed, but those three pilots where neither inexperienced nor stupid.
And reducing your speed isn't always a solution, because at lower speeds a helicopter is less stable.
I can tell you from my own experience, that sometimes it just takes a second to get into very dangerous situations just because you look in the wrong direction. I admit, that I should have turned around way earlier, but 30 seconds before that, the situation wasn't all that bad and I could still see for miles.
Never ever follow a more experienced pilot because you trust him. Take your own decisions.