In reply to Northern_Monkey:
Generally nobody is responsible for making safe loose rock on an outdoor climb, as a climber you have to accept there may be loose rock, keep an eye out for it and be prepared to act accordingly if you come across it.
What is a good idea is to help your fellow climber by reporting anything particularly dangerous which you can do if the crag has a wiki or on here on the climbs logbook page. Sometimes a public spirited climber or BMC volunteer will remove a loose block but this is by no means a given.
Don't let this put you off, I've climbed for nearly 30 years and only fallen off a couple of times because a foot or handhold has broken off. Spotting what's OK is part of the skillset!