Photographing a Wedding With a Single Lens?

As a wedding photographer, it can be easy to justify a large number of lenses for different purposes throughout the day (35mm/50mm primes for getting ready, 70-200mm for the ceremony, 105mm macro for shots of the rings, 85mm for portraits, and so on). In reality, most weddings can be documented well with significantly less gear. But how much less?  I recently had someone ask me: “For someone looking to get into wedding photography, is there a single lens that you would recommend that would be good enough to start with and be able to shoot a full wedding with?”