Good discussion.
I think it's like a lot of things in life: Get knocked off your bike without a camera... or get injured because of a badly mounted camera... and either way you'll regret it! :crazy
Personally, I've no qualms if folks use them for fast road or track use, but if they distract, or cause the rider to take risks just for good effect, they are dangerous.
But I always find watching a video of a bike run is no where near as much fun as the actual bike run!!
And hey! Summer is here this week (in UK), with 30C forecast... so ride safe and enjoy:thumbup