none of those videos are at 800 feet and it sounds to me like the excited reporter probably should have said 400 feet to be more accurate with a comment about flying at the top end, not because the video is at 400 feet but because someone mistook the top end.
six, as you know, the pilot may see 800 on the controller but isn't actually 800 agl hence there could be confusion when you have a bunch of folks discussing the incident and not knowing the facts. area looks flat but you know what i mean. also, i (anyone) absolutely can see/hear my e2p at 400 feet agl, you're joking right? if i am going to hide from the unaided eye, i'll need to be closer to 1000 feet to be sure...i found that out in mexico 5 years ago.
as far as part 107 (im going to be controversial here), you need a part 107 if when you take off, your flight is not for fun and in furtherance of a business. if you take off for fun and 5 minutes into a flight, you start to notice unusual activity so you go hunting and searching, it's still a recreational flight because your intent when you took off was to have fun. the flight doesn't change into a part 107 half-way in the flight depending on what happens during the flight. however, if you drive to the nearby park and you launch your drone so you can get a closer look into a fenced in yard to see what these guys are doing, not sure if that's in furtherance of a business; debatable.
still, i believe the bigger picture here is police use of drones. this forum/thread is probably not the place but imagine if police can fly drones without a warrant and look around in order to develop probable cause....personally, i would never go to the police with this video and as you can see, police aren't even bothered/don't care.