There is a great deal of media hype associated with the term "extreme sports" to be sure. Webster.com provides the following:
exÃ‚Â·treme 5a: of, relating to, or being an outdoor activity or a form of a sport that involves an unusually high degree of physical risk.
Our individual definitions and perceptions of what constitutes "... unusually high degree of physical risk" is going to vary substantially.
I use the term for one primary reason and it has nothing to do with hype. I use it as a warning at least to those that pickup on it and think about it. Kiteboarding is a potentially dangerous sport and may currently have a higher severe casualty rate than paragliding and perhaps hang gliding. Global statistics for these other sports don't appear to be readily available.
If you are careless, unlucky or are going out in conditions beyond your abilities, kiteboarding can be very "extreme" and hazardous. It can happen in relatively light wind, see
for only one example of MANY that could be offered. Higher wind, waves, cold temperatures, etc. do help however to pump up the risk and consequences of misfortune however.
If you practice reasonable care, use good technique and safety gear the hazards may often be reduced. Personally, I consider kiteboarding to be the most dangerous thing that I do out of hang gliding, aerobatic flying, deep free diving, trimix diving and tree snowboarding. It all comes down to the incident/accident experience.
From all that I have experienced, read and written about, I consider the warning justified and worth passing along. Hopefully folks will consider it for what it is worth.