We had an OH58 in Germany come back one day with kite string wrapped around the push-pull tubes. The pilot swore he hadn't been below 1500'.
I once encountered one over the beach as I flew along under 400' overcast, trying to find a place to beach out to get to a platform about 3 miles off the beach. I was in an AS350D, and I banked it almost 90 degrees to avoid the kite that suddenly appeared. On the way back, I was looking for it, and didn't see it. Then there was a break in the clouds, and I saw it flying
above the cloud layer! Put it on its side again, cursed, and somehow missed the string.
I also saw one flying at about 500' or more at the airport. We finally tracked down the owner, who claimed to be ignorant of the dangers.