Always depends on your situation. If I'm a young breh. 20's/30's single, no kids and that could get me some good experience? Hell yea.
If you're talking about a job in general when you don't have one or the contracting job pays significantly more than your current job, then yea. But if the contracting job only pays 10k more compared to the employee job and you're making 50k+, no way do you leave the employee job.