When I’m shooting events, I will often do 500-1000 pictures in a day. My Nikon D40 is fine for web work, takes about 1000-2000 pictures on a single battery (I have two), and, best of all, works with all my Nikkor lenses from my two Nikon film cameras (although I have to set the aperture manually with a couple of them, and focus manually with all of them). When I was using film, I’d usually shoot 2-3 rolls per event. The multiple pictures are especially useful when shooting people, because I can always get one with the “right expression.” Otherwise, it’s just being careful. One thing I like about digital over film is being able to change the ISO on the fly; when I used film, I used to bring 2-3 film cameras (my two Nikons and a good quality/no frills Canon point and shoot) and one digital camera with me; the three film cameras typically had 100, 400 and 800 film in them (the 100 film I used in the Nikon with the better flash).