While I don't know if I'd ever do that, Kite Boarding is entirely different than Kite Tubing. Kite Boading has been around for years.
Kite Tubing is just a wide tube and high speeds behind a boat so I agree Spencer, wouldn't do it.
Kite Boarding is closer to Parachtuing. No boat, nothing draging you around but wind and you have about the same level of control as a sky diver.
Would I go that high? No, I'm a wuss.