An essential trait (purpose?) of a "blockbuster" exhibition is its transcendance above the museum's normal day-to-day operations, and more importantly the museum's public image.  Has a poll been taken to research the number of "blockbuster" visitors that have not been to the said museum since the last "blockbuster" two, five, ten years ago? Blockbusters allow museums to flicker in the minds of those who are not normally part of the museum-going population.  

The recent Van Gogh exhibiton here in DC is a good case study, and an example of how the early 1990's prophesies of the "end of the age of the blockbusters" did not come true. Hour long lines, massive media coverage, front page coverage in the Washington post (as well as an issue of the Post's Sunday magazine dedicated to the exhibition), permanent collection gallery space turned into a temporary museum shop, etc, etc,--Van Gogh, and exhibitions like it, temporarily redefine museums, making them more popular, more talked-about, more visible.

Oddly (sadly?), in the midst of such out-of-the-ordinary attention, the National Gallery's permanent collection galleries, and even some of their exquisite "non-blockbuster" special exhibitons seemed only somewhat more habitated than usual. On a weekday, during Van Gogh, I visited the NGA's Bernini exhibition to find it virtually empty, while the lines to enter Van Gogh wrapped around the building. 

Articles have been written on the positive and negative effects blockbusters have on the every-day operations of museums, I remember a few such articles from about a decade ago.  An interesting area of study might be something like: "Blockbusters: temporary phenomena or standard/primary function of museums?".