CS and Econ PhD programs both benefit from an extreme amount of cross-pollination between academia and industry. The ability to jump ship from the academy isn't nearly as large of an issue as it is in the sciences (with the exception of physics perhaps). The humanities are mostly screwed.

Source (for econ at least; CS is anecdotal): http://noahpinionblog.blogspot.com/2013/05/if-you-get-phd-ge...

Not from what I have read or heard. There still seems to be a need across the board for those with deep knowledge, especially when it comes to certain topics. The people I have known who have had trouble, and studies I have read about the topic point mainly to biology and chemistry as the two hardest fields to break initially with a PhD. But of course even that could change depending on specialization, etc.