An important point is that if people drone along on exactly the same track and don't change their height or speed, they're setting themselves up for a "fly on the windscreen" type incident, or worse. Especially if other pilots are doing the same thing plus the state of the windscreens on a lot of GA aircraft I've seen doesn't help...
I fly power aircraft and gliders and given their low frontal area, the density near launch sites or airspace funnels and the close proximity gliders routinely operate in, glider-on-glider events are comparatively rare, some of which is due to the reverse of the above effect. FLARM has extended the "lookout" to places you can't see, as well.
It's a shame that the laws of physics have conspired to make the most difficult target to spot the one that's most likely to hit you but that's how it is.