Tight formation can actually be easier once the skill set is in place. Loose formation has the added danger of losing sight of the other aircraft whilst doing a FREDA check or similar. Looking up and realising you cannot see the lead aircraft is somewhat sobering and is possible even at 300m. Everything then snowballs very quickly.
Indeed
Yesterday the Swedish AAIB released the report for the midair between a C-172P and Saab Safir during a Civil Air Patrol (Somewhat similar organization) exercise. Cessna was doing a search along a power line, with pilot and observer on board. The Safir was flying chase taking pictures of the flight. (Pilot and 2 photographers)
Everything was briefed, and the Cessna was lead, and told not to worry about separation, the Saab would stay 100m to the left, 100m to the rear, and 100m above the Cessna.
During a turn one photographer in the Saab got ill, and the pilot attended to him. Seconds later he spotted the Cessna passing below him, and instantly heard a bang as his left wing struck the tail of the Cessna.
Now, both planes landed safely at nearby Østersund Air Base, the Cessna with a jammed rudder.
3ft lower for the Saab, and five people would most likely have perished.
For scandi readers:
http://www.havkom.se/virtupload/news/rl2007_19.pdf