I have no problem with it. The New Yorker covers are genius and this is no exception. I can't wait to read the story.
Also, this is classic Barry Blitt. His work is often hilariously shocking.
As for the repercussions of people walking by seeing it, The New Yorker has, for many years now, had a 1/2 vertical page with story titles and page numbers on it. It heavily obscures the cover illustration. This is done to boost newsstand sales, since they've never printed words on their cover other than the title of the mag, choosing instead to feature a full page illustration.
So, in other words, unless someone picks up the mag to look at it, they're not going to see much of the illo, just the upper right corner [assuming the newsstand itself will obscure the bottom portion].