Cameras rarely specify exactly what speed cards you should be using in them - I just checked the manual for my DSLR, and all it says is to use an SDHD card, and a "high speed" card should be used for recording video.
On the other hand, there are a number of different rating systems for memory card speed (33x! 150x! Class 2! Class 10!) and price seems increases with speed.
Is there any way to test the maximum write speed the camera is capable of? Are the read/write speeds documented anywhere?