That would be another reason for shakier footage then. Given its size, its best to shoot using the higher frame rates as it creates much smoother motion.
Just as an example, I've been editing some footage from two Hero2s. I was using 720 @60fps on mine, while my friend was using 720 @30fps. The difference is significant, as the footage from my camera is far smoother.
Obviously there are a couple of caveats. The higher frame rates obviously use more file space, but I found shooting at 60fps its fine. The other is that you want to use a lower frame rate in darker environments, so underwater a slower frame rate may be beneficial so that it doesn't up the gain if its really dark.
Also worth pointing out to anyone who doesn't know, you can access higher framerates by switching from PAL to NTSC in the settings. Its largely irrelevant these days as TVs in the UK will play back NTSC framerates just fine these days, plus most people are uploading to the web anyways where it really doesn't matter.