I watched a wedding photography seminar this weekend.  She shoots using four lenses – 3 primes and 1 zoom.  The zoom is a 70 – 200 f/2.8.  The primes are a 24 f/1.4, a 50 f/1.2, and an 85 f/1.4.  She shoots everything available light, only using flashes rarely to fill.  Thus the need for such fast lenses.