there is nothing wrong with quitting.when i had an internship with citadel lined up almost two years ago my advisor threatened to kick me out of the program if i take it.so i stayed. just to end up in this job market.if the right opportunity comes along, take it.

Perhaps in the early stages of ones PhD it might be feasible to quit and not for it to have too much of an impact on your future career. But, I would strongly recommend you finish the PhD if you are nearly at the end. In this job market those with PhD, on average, progress further. Sure there are cases where those just with a good BSc have done well and progressed further, but such cases are becoming rarer in such a tough market. I know of a few even with PhDs and still find it hard to break into this market. The competition is just too high now in comparison to say 10 years ago when there were relatively less PhDs to swamp the market. Now I think a PhD is fast becoming a standard for quant jobs and a filter and rightfully so since it takes a huge amount of dedication and hard work to finish one. If the worst comes to the worst you can always write up for an MPhil, but it will look like a failed PhD to some who know the system well. Otherwise you have to account for a few years in academia for a failed PhD, and that is not be easy. StatsGuy