I personally found formation flying very enjoyable, and its value in tactical situations essential. I can't think of any use for it other than military or paramilitary operations.
One of the most chilling helicopter collisions I ever saw was the two Super Pumas about 7 or 8 years ago doing a formation flypast in Kuwait, I think. The discs touched and it was quite gut wrenching to see the machines disintegrate like that.
Anyone else remember that?