I knew one dude in high school who was a certified mathematical genius. Like USAMO finalist-level genius. But he never finished college, and Google indicates that he died of an overdose a couple years ago. The dude was an extreme autist who did poorly in school because he thought that the homework was too boring. But I never thought that a USAMO finalist would flame out that spectacularly.

I know another guy who won a number of major math competitions and graduated with basically a perfect GPA and SAT scores who ended up getting a BS and MS from the local TTT and now has some grunt job with the military. Not an abject failure, but certainly less than we expected from him.

I also know a dude from my high school who went to a T10 law school during the early 2000 boom days and did a prestigious clerkship afterward. But within a couple years he was doing shitlaw in a flyover state then went solo in the flyover state. Last I heard he is out of the legal profession and selling real estate.

That doesn't include a number of women I have known who had spectacular credentials but disappeared after forming baby. Personally I think there is no shame in this.

None of these people were particularly "pretentious." One was an autistic weirdo but still nice enough, and the other two were very cool guys. They just happened to be the most spectacular flameouts I could think of.

(http://www.autoadmit.com/thread.php?thread_id=5118808&forum_id=2#44591151)