The 30m (100ft) rule here in Australia may be similar to other places. Or it may not. The 30m rule is diagonal, not lateral. In a phone call to CASA the other day, I learned it's not what most think it is. I was always under the impression it was a lateral distance. I could be 300 ft high, but laterally I would still need to be 30m away from buildings, people and vehicles. Not so. According to the guy I spoke to, it's 30m diagonal or direct. In other words, if I was 31m directly above someone, then I would still be within the rules. He did caution of course. He said it's all about risk, and if it was a crowd of people then that risk would be substantially increased. Also, when a UAV malfunctions, it won't always just drop straight down. It reminded me of when my Phantom span off (probably a ESC issue) and hit the ground hard, about 10m away from where it lost control.