getting blacklisted is a BIG nono.. it makes your life much harder .. some ppl wont even look at ur resume if they happen to know ur blacklisted

must be not doing the job well

he is just lucky then.

usually a high reputation company must do following steps (Standard Operating Procedure) which involve getting reference letter from the previous company the candidates work for. you are able to not write in your previous employment but what if they ask what have you done during this time (during your previous employment), should you lie that you have done nothing or tell the truth but for unknown reason you did not write that in the resume and at risk of getting a not so good reference letter from previous employer.

but like said, reference letter isnt important for some company while it is very essential for some.