We dirtbike and I really think that 30fps is all that is needed. This would include wakeboarding. Now, if you wanted to get all "poetic" and do some deep slo-mo wake splashes, then 60 fps would be the ticket.
However, in my mind 30fps does not mean the same quality for all cameras. Not sure what you're looking at buying, but I have enjoyed my GoPro Hero. I have been amazed of the quality of video and the ability to take a single frame (from the movie) and make a 8x10 photo with it. It is crystal clear. The only problem is the fisheye that the camera has and it is much better with more light. I shoot most helmet cams and pics at 960 which gives me a taller view so if I make a mistake aiming on the helmet, it is usually still okay. However, for wakeboarding and boat, when I use my LCD, I'll prolly go 1080 at 30fps. It will not shoot 1080 at 60, but I just don't think it is needed. If I shoot 60, I have to go 720.
More info than you needed. The Hero2 will shoot up to 120fps.
Here's a video I did recently. Did kind of a retro 80s, North Shore theme. When my son is riding in the area alone, with me shooting, I grab a frame of him jumping with the sun behind him. Not sure if the video will show all the detail, (prolly won't) but the pic is attached. It's pretty good.
from Big Johnson Productions on Vimeo.
Here's the frame I grabbed from Sony Vegas.