A lot of places require 2 weeks notice to be paid for your accrued vacation time etc. If you leave without giving notice you could risk that payment. I have witnessed employees give longer notices to their employers to help them find a replacement only to no longer earn vacation time etc during their time left at the company.
that being said, the company I work for is very good about making sure there are no suprises. They will let you know months in advance if your work is not fitting in with the rest, or meeting expectations.They will also let you know if a work slowdown is coming and there might be a lay off. To my knowledge, the two lay off victims were given a month severance, and the one person who was let go with no notice due to his impact of office morale, was given a good severance as well.
