Why have Ministers and Preachers stopped preaching on Hell? Back in my early years it seemed that every other Sermon was about staying out of Hell. Now it seems that you never hear any Sermons about how terrible it is there.

As a young child that scared me and began my quest to find Salvation.

At a recent Sermon the minister even said that the result of sin was eternal separation from God. And while I agree that that is a part of the punishment, I do not feel that it is any more horrendous than burning for eternity in the lake of fire and not being able to die.
My answer? Churches nowadays are unfortunately often focused on quantity. "We have X churchgoers" or "Our denomination has X followers". They preach in order to get more people to attend and come back for the next seremon.

Preaching about "controversal" subjects loses followers, as we can clearly see from the Gospel itself - John 6 from 53 on, where Jesus talks about eating flesh and drinking blood, which resulted in 66 "From that time many of his disciples went back, and walked no more with him." By the way, Jesus was not about quantity - his reaction was in 67 "Then said Jesus unto the twelve, Will ye also go away?"

You can also recount the fate of John the Baptist. He preached to Herod about his unethical sexual relationships, and where did it got him? 

I'm from Russia, and we had a similar case recently. A priest Daniel Sysoev http://en.wikipedia.org/wiki/Daniel_Sysoyev (arcticle is short, if you want to know more, better read its russian version through google translator, since it's got more content). 

He preached very radically and with disregard towards how people will take his word or be offended by it. He was not shy to speak about hell, and how muslims and atheists and gay people will suffer eternal damnation if they do not repent, he was not shy to state boldly that Christianity is the only true religion, and the only one that leads to salvation, he was not shy to state that God does punish sinners. He made huge missionary effort, he converted many muslims to Christianity. 

What happened to him in the end? He was assasinated, shot in the chest in his own church building by a radical muslim. Many people regard him as a martyr.

I think this answers your question very well. Preaching about controversal subjects is hard, and requires a certain degree of selfishness. And gets you in trouble.

PS: 
Finally, Hell is a hard subject to talk about because it has so many meanings entwined and attached to it. The term may very well be misunderstood by the modern society as some sort of prison for sinners, made by God to punish them, which it is not. So it may be a good idea to explain the concept without using the word.