I have enough references and having two jobs at any given moment does offer me that extra leverage not to take crap from anyone.
Though I did stick around at a place longer than I really should have due to them screwing me over my back and not back paying me TWICE. The company seems to have a habit of going back on their words, or stringing you along, changing management and saying "oh you're agreement was between you and him, not you and I." type crap. Now I learn to get things in writing. If they don't treat me fairly, why should I? And if I'm tired of your crap why should I force myself to deal with you for another 2 weeks?
And at another place BEFORE I even start I'm up front with you my circumstances under which I can and cannot work, then only to have you to tell me that because of how schedules work you will now have to work from so and so to so and so, but I'm sorry that doesn't work for me. I told you my availability before I even started, no excuse. When you ask to stick around or wait til the person from the next shift comes in and for them to be ready, or if they're late for whatever reason, you're making me or asking me to stay late means I will be late for my next job. No can do. They're desperate for people, bring me on, only to go back on their words afterwords. Don't pull that crap on me, cause in the end it will only screw yourself over, which it did when I told them "sorry, but today will be my last day" and end up having them scramble to cover for my next night shift.
And when they fire you within your 3 months or whatever amount of days of probation, they don't give you two weeks notice.
Depends on the field of work too I guess, some can't afford to cause it's a small field and word does get around.