I'm a bit late to the party, but there have been discussions lately about the number of undergrad STEM majors, including physics, with some gnashing of teeth about overall difficulty. For example, a report by the National Bureau of Economic Research has been interpreted as saying that the main reason students bail on science majors is poor grades. That is, students go in, knowing that science will require more work than majoring in something fluffy, but when many receive tough grades even though they work hard, that's too much for them and they change fields. Chad Orzel does his usual thorough job looking into what the study really says, and it does seem true that tough grading drives some people out of STEM pursuits.
Similarly, there is a new report from the National Academy of Sciences called "Adapting to a Changing World: Challenges and Opportunities in Undergraduate Physics Education". I found the content rather disappointing, in the sense that it didn't seem to say much new. We all know that some approaches can be better under some circumstances than traditional lecture. However, many of those are very labor intensive, and I'm sure that my 50 person class would benefit if it were instead five ten-person classes. More to the point, though, the report specifically claims that hard grades are a major factor in the low participation of women and underrepresented groups in the physics major.
So, is physics unnaturally harsh in its grading, to its detriment? Or is this a question of high school preparation on the one hand, and grade inflation in nonscience majors on the other? I lean toward the latter.
(Note that the NSF has proven that science is hard. Also, here is the paper featured in that article - it's actually very interesting.)
(One other note: no one commented on my three part post about the physics of contacts, and the hit rate on those posts was very low. At the same time, in one 15 minute interval last week my post about "whiskey stones" got nearly 500 page views after it was mentioned in an argument about whiskey on reddit. Guess I should write about other things besides physics if I want more readership:-).