I worked at a large health insurance company for nearly 10 years. I was pretty gung ho when I started there but the place slowly wore me down. Horrible management (except for one person) that lied to it's employees (about important things like "Are you going to move the office to another town 90 miles away?") while slowly outsourcing our jobs to India.
They would fire people by waiting till the person left the building to go to lunch then have their supervisor box up all the personal stuff at the desk and meet them when they came back from lunch, in the lobby, to hand them their box and take their security badge. I saw many nice people walk away crying.
When I finally had enough and got a different job I just called my supervisor the day before I was starting my new job and said "I quit". I have no qualms about doing so either.