On the one hand, I've often wondered about the "fringe" runners, who probably stand very little or no chance of breaking thru, pressing on with full time running. And while I'm someone perfectly willing to judge, my wonder was/is of a non-judgmental type - kinda like "Geez, that's too bad (that they'll struggle for little and possibly no pay-off).
But to read some of the jerky comments here judging these folks is annoying. First off, don't pretend that it's ANY sort of objective truth that pursuing a low/non-paid "pipe-ish" dream for a good handful of years after college is "stupid." It's not, it's a perfectly defensible decision.
Moreover, these "I'm so smart and pragmatic (and yes, materialistic) about life" types also display how little they really know about how lives can and do play out. The fortunate reality is that one can endure a whole bunch of "lost years" (financially speaking) in your 20's (and probably often into your 30's), and still enter middle age in fine professional/financial shape. Line up some number of thoroughly comfortable 50 year olds and their trajectories to getting there will vary a lot. Life is plenty long enough to be thoroughly un-materialistic in your twenties (poorly-returning time in grad school included) and still wind up perfectly fine.
Oh, and lastly, I think that we're largely talking about 2-teens type talents wondering if they can go 2-ten or under....NOT 2:30 types who MIGHT be 2:19 types. Most serious runners would kill for that talent, but it's still not relevant to this discussion. Sorry, some of you "tough" and insensitive guys.....