Basically, he claims that working in an amoral environment will eventually turn you into a worse person than you would otherwise be, and weaken your resolve and desire to fulfill your original goal.
This is a valid consideration, but that is partly why having a lively community of effective altruists is so important, as a way to prevent value erosion.
I am going to quote in its entirety a comment at Hacker News. Jason Trigg is the young philantropist referenced by the NYT article.
I went to college with dozens of Jason Triggs (including myself). We'd talk all the time about the money we'd make right out of college and how much good we'd do. ("$36k to work at a soulless consulting company? That's amazing! I'm living on less than 1k/month in college. I could save 5K and give 10k away and not even notice!") We had plans to give 20, 30, or 50 percent of our income away. Some of us even managed to do it for a couple years. The world gets to you, though. Your coworkers that dress nicer and go to happy hour with the boss get promoted. It gets tiresome to commute from a tiny apartment in New Jersey. You buy a house or get married to somebody who doesn't make much money. The stock market tanks and takes your savings with it. You figure out that you hate consulting and end up teaching science in a junior high. After a couple years, I'd bet that the average charitable contribution of my peer group had gone down to 5% or less.
I wish Mr. Trigg luck, but we've already lived his story. He might get a few good years in, but his life is unlikely to work out like he plans
The point about pyschology changing may be valid. Unfortunately, Brooks spends most of the piece not actually discussing that issue but rather other (substantially weaker arguments). For a large portion of the piece I just kept thinking "and that's bad why?" It seems strongly like he has his bottom line already written.
Just wanted to highlight an article. David Brooks from the NY Times writes on earning-to-give by working at a hedge fund:
http://www.nytimes.com/2013/06/04/opinion/brooks-the-way-to-produce-a-person.html?ref=opinion
Basically, he claims that working in an amoral environment will eventually turn you into a worse person than you would otherwise be, and weaken your resolve and desire to fulfill your original goal. Psychologically he may be right, and today's me may not like the me I would become after a decade on Wall Street, but at first glance it seems like even if I could only maintain my resolve for a few years, the payoff far outweighs my own well being. He is also opposed to valuing the far - life in general - over the near - people in your own home or community. Or even valuing them equally, AFAICT.
As a matter of history, though, I did not in fact choose such a career. Suboptimal or not, given what I did choose (consulting firm that helps companies invest and grow effectively in clean tech, nanotech, and biotech) I do not think I chose wrongly.