Sat Sri Akal
Veerjee, I think like manbir pointed out its all in the head.
When you do something wrong, you know that you are doing wrong, but still you go ahead and do it. I guess at that time you are in yamlok and the possible repercussions you think it will have is the yamraj and the saza for that.
Apart from that, what the gurus are pointing out with reference of yam in different verses is that end is near. And also since the gurus were preaching in the language of the common masses and since every one believed in yama, it would be pointing that Yama is always watching you, or is sitting on your head like a coiled snake. So as to shake a man up and lead them to the life of meditation and god.