Chris has already commented on Drezner's post about low retention rates at graduate school, but as a bona-fide grad-school dropout myself (ABD in philosophy, 1997, University of Rochester), I just have to put my two cents in.
I dropped because after five years my funding ran out, my dissertation on Kant's Theory of Substance was going nowhere, and the job market was looking awful. Why put myself through it anymore, when the newly-minted PhDs I saw were teaching multiple part-time gigs at Monroe Community College and St. John Fisher, and making less than I was making as a TA? So I ditched it all to become a computer geek, and seven years later, I’m doing better financially than I would have teaching. I’m making an upper middle-class income according to the Calpundit scale, and I’m living in a city that I like where there’s very little snow.
I’m not bitter, and I have no regrets except for not shooting higher in terms of what schools I applied to. I had the chance to study with a brilliant metaphysician, who was also an excellent teacher, and even got two footnotes in his book. (Even if, due to a typo, one of them reads “Sider (1997)” instead of “Sides (1997).” Grrrr.)
I could have spent 1992–1997 working some job I hated, trying to figure out what I wanted to do. Grad school was a fun way to kill some time, and it’s better to drop out of grad school with very little debt than graduate from law school with a huge mountain of debt, only to discover you hate practicing law.
So go on and go to grad school. But don’t get your hopes up about a career in academia. Have a back up plan.