I know of one person who left. She had a degree and some experience in something else, I think engineering of some sort. Wasn't happy flying, and got a job with an oil company for a lot more $$. I think she was one of those for whom flying became work as soon as it became her job.
I am seriously considering leaving within the next year. I previously drove trucks to pay for flight school. After 7 years in aviation, I'm still $10K/year short of what I was making in the truck. Given that I have no jet time, and refuse to work for an RJ FO's salary, I have very little expectation of ever moving up in this industry. I'll sure miss the flying, but having some extra money will be very nice.