Doesn't necessarily have to be 32gb (a 8gb card will give you about 23 mins of recording at 1080/720p HD), but make sure that it's at least class 6 and a reputable brand, go for class 10 if you have the extra coin.
Cards lower than class 6 might not be able to read as fast as the camera's trying to write to the card and the video will stop recording. Though if you buy a legit brand, class 4 may be able to record video (my Lexar Platinum II 8gb class 4 will record video on my t2i, but my shittier Silicon Power 16gb class 6 won't cut it for recording video.