I've got a group of friends who launch high altitude balloons quite frequently. The put cameras and other sensors on board and aim for the edge of space. They study weather patterns etc so that they can recover the balloons and equipment. Most land withing 75 miles of their launch site and they coordinate with the FAA to avoid interference with aircraft.
Don't recall if I read it in a book or heard it in a speech but former SR-71 pilot Brian Schul saw something ahead of the plane during a flight one day. Before he could discern what it was he rocketed past it. Using the rear view periscope in his canopy he saw that it was a weather balloon and the wake of the Blackbird had upset the balloon quite a bit.