Couple young guys down here regularly fly their kiteboards (basically a snowboard set up to run on the water, with a serious parasail and bombproof harness on the body, controllable using the shrouds) on the Clatsop Beach, sometimes in surf, sometimes in the major backwater inside Trestle Bay. They appear to be in control up to windspeeds of about 30 knots, ramping down to sails of smaller area as the wind rises, primarily operating at the water's edge and sometimes in 4 foot surf, max.
These guys are extremely strong, very fit, and very safety conscious. Even so, they are very aware of the risk, and are quick to shut down when conditions get out of hand. And, it is an easy swim and easy retrieval if they crash.
In contrast, off Manzanita, from the Neahkanie Mtn overlook on 101, you can spot guys using similar rigs, running inside, through, and outside the surf zone, out a long quarter mile or more, onshore winds. With a long swim to shore, no way can they retrieve a sailrig if they crash. No Waverunner patrol. Nothing. Freaking nuts!