<p>A B grade is not a bad grade if your goal is to graduate from college, and many careers only require a college degree. If one wants to find employment as a physicist, however, this really requires a PhD. And if you want to go into academia, you need to not only get a PhD, but a PhD from a good or top graduate program. For admission to those sorts of programs a B-, even at Harvard, is not good.</p>
<p>I have not read Gladwell’s book, but I think it is far more likely that the students in question found fields that they were good at. I was an undergraduate physics major for a while, and discovered that while I enjoyed physics I was a B physics student. I found a field I enjoyed and was able to do well in, well enough to go to a top 5 PhD program.</p>