I've been a fan of photography for 17 years, and I've taken countless pictures on beaches (and quite a lot of other places!). The reaction all depends on how you approach both the subject and locations. I've seen photographer be roughly handled but it appears I've been doing it well since that never happened to me. Always respect the privacy of the people and they will respect you. Quite often people will even come and ask to have their picture taken, in which case I simply email a link to their private copy.
Sometimes you get a nice shot of a non-descript couple or something, in which case if I get the chance I'll go meet them and present the result, and ask if they want it (free of charge) and everyone has been happy so far.
I recently started playing with a quadcopter, and the result is the same, except that I have much more inquiries and people want me to video them and give them the youtube link. A lot of people where very happy to get to see the world from an higher point and I've received countless thanks for this already.
Also, keep in mind that most drones have a very wide field of view, so you are very small in the video when the drone is still pretty close. About the girl waving, it's entirely possible he was taking pictures of the house/property around, and when he noticed someone he flew out, since you must take all precautions not to fly too near to people.
I've also met other people flying their drones, either custom made, new products being developed or commercial ones and everyone I've met so far were nice people. I find it nice that people get together and talk because of this new subject rather than each of them taking selfies / ignoring everything around. Oh well, your mileage may vary :)