With the low cost of remote drones with gimbal cameras the uses for crime or terrorism are almost endless.
Many years ago a local major criminal employed microlights to monitor police activity and responses to crimes. These days a few remote quad copters could do the same, give real time images as well as being harder to detect from the ground.
A quad copter over Wimbledon may just be taking pics (but not innocently given the times we live in) but could just as easliy drop something nasty over the court or crowd.