Let say, Guru A give you a simple buy call tips :

Buy X at 2.00, TP 2.30, SL 1.85, risk reward  1:2 - simple and easy, everyone can follow, right ?

You have follow Guru A for sometimes, and you have earn some money from his tips, and so you follow again.

Then this time X suddenly collapse in a very short time, by the time you know it, it already fall 30% to 1.40, way below your SL. Even if you have told you broker to sell if it fall to 1.85, by the time your broker put in your sell 1.85, it might already have 5000 in queue for sell, but not enough buyer. And bcos after a few small won following Guru A, this time you put in a big gamble think it will sure win as usual, but you get burnt and lost badly, not only lost your previous winning, but lost the money that you can't afford to lost as well bcos you put in too much trust on Guru A.

Then you ask Guru A, But Guru A tell you, bcos of some change of circumstance, he has already cancel his trade much earlier before the collapsed. He say he just giving tips on free basic, so has no obligation to inform everyone, or he is busy no time to inform everyone. 

Another real story on forex Master :

Master B teachimg forex class, and sometime he will trade live togther with his student, when he lost, he said it was a reasonable acceptable lost. But then, there was for him, not for some of his student that think Master B is godlike, and bet in bigger than he afford to bcos put too much trust on Master B. And a few students who who happen to be maths genius and programmers, they back test every techniques of the Master's techniques, the result is no better than you random pick :D

- while you can follow anyone you like, but you still reponsible for your own trade :D