It really is up to the employer. If people will give 2 weeks or any notice at all. If you were a fair employer, treated people fairly and with respect, didn't try to cheat them, paid them for all work done, etc then people will want to leave on good terms. If the employer demeaned them, didn't respect them, worked them hard and tried every loop hole to try and screw them regarding pay, overtime, workload, then people not think twice to leave them high and dry if a better opportunity comes along. A former employee may not get a reference but a bad reference or disparaging remark by the former employer that prevents a person getting a job is grounds for a lawsuit.