I personally know many people like this (Niyyas's) thought of school, who are now " back to India" or in process of cancellation. and now they and their family members calling and requesting for giving them one and last opportunity again.
One guy was more smart, after one month long processing,interviews, telephone calls, signing contract letter, and getting visa copy he suddenly refused to come and said that he has very serious family problem and even he swear to God. Employer said ok. right after 2 days that guy called again and you know what ? he apologies for telling lie, then he start to requesting plz I have another company's good offer and I wanted to join that company. but due to visa is withdrawn by you I cant join that company....lolz

Career growth and looking for best wage is right of every body, but after making commitment with one company who is investing its time, money, and whatever resources they have it Truly totally unfair and very bad to break your commitment. so Always first think carefully and then join anybody... don't wast others resources, time and hopes after making commitment