How many do you carry for a shoot and what size? I've just bought 2 16Gb sandisk class 10 cards, It seems like overkill, but I plan to start shooting RAW soon, and assume the extra capacity will come in handy!
with my D800 shooting RAW a 16 GB card holds 200 shots. I am finding the 32 GB is more usable and if it is to be a heavy day I can load 2 32's (1 SD, 1 CF) and have 64 GB good for about 800 shots which is really great for a full day shoot.
That's what I have, 2 16's. I have the d7000 that allows me to have two cards in at one time and I have never come close to filling one of them up. I shoot RAW also, but I do spend my weekends at tournaments and want to make sure I have plenty of room.
With the second card serving as an overflow then I can get around 800 shots combined