No, I don't mean the bagel shops. Why do towering scientific geniuses seem to be a thing of the past? There are many potential reasons, but one fascinating aspect of the question is addressed by the physicist/historian Silvan Schweber, in his new book Einstein & Oppenheimer.

I believe there are always people like Einstein about. I believe that Julian Schwinger, Richard Feynman, Murray Gell-Mann, Frank Yang, Steven Weinberg, Gerard't Hooft, Kenneth Wilson, David Gross, Edward Witten, and Frank Wilczek are such people. The fact is that the range of phenomena they had to deal with was much more extensive and the amount of reliable, accurate data they had to assimilate, comprehend, and explain was much greater than what Einstein had to confront with his gravitational theory. Also, their community was and is much, much larger, and the competition they faced much more intense... Given the size of the community, the selection process that operates in the choice of scientific fields that attracts gifted young people, and the cultural context, perhaps it is not possible for an individual at present to attain the "mythical" greatness that Newton and Einstein were able to achieve. Schweber, p. xii

I'm inclined to agree - the scientific community has grown and become professionalized, rendering it substantially different from what it was before WWII. This argument is similar to the late Stephen Jay Gould's , who used the disappearance of the .400 hitter has his example. Schweber's book is more than this argument. He's got much more to say about the role of personality, culture, and comminuty in an individual's scientific success - this is a book worth checking out.