I personally wouldn't, the GBR has enough of a hard time with over enthousiastic tourists, fishermen, the fishkeeping hobby and crown of thorns starfish.
I know there are some that would say that as fishkeepers it's no different to going to a shop, etc but the way I see it, the fish/corals/liverock/etc in a shop have already been collected so why should I take more from an already exploited and fragile system? Besides, even fishstore suppliers are only allowed to collect from certain places at certain times of the year, etc. If they are regulated and forced to conduct their trade in a way which has the least amount of impact to the enviroment then who am I to just waltz on down to any place I want and rip up chunks of habitat willy-nilly. We create a percentage of disruption to reefs as it is so as fishkeepers we should be responsible enough to limit that disruption as much as possible for the good of the enviorment, the organisms that live there and ourselves as well.
Just my 2c worth.