Where do you draw the line?

I was reading up on the recent accidents and one had me wondering.

This was the damage to a K13 at Buckminster in the UK on 15 January. You can
read about it here -
http://www.gliding.co.uk/accidents/d...dentSummary=23

It appears from the accident report that this was caused by a retrieve driver
who was totally oblivious to the consequences of his actions. His lack of
situational awareness nearly killed two people and damaged a glider.

Now I am not in a position to comment on the behavior of the person responsible
for this incident, but it got me thinking on he principles.

So the question is - Who decides when someone is dangerous on the field? Are
there generally accepted principles for when a person is permitted to perform
potentially dangerous duties? Who has the authority to say?

At my club, the CFI is the final arbiter, and has politely relieved at least one
person that I know of, of any duties where other club members lives were
perceived to be at risk. Maybe we were wrong, he still gets to drive the
retrieve...