A few people would regift the corals, macro, snails etc once they got established and its funny usually you ended up as mates with those people and will end up helping each other out whenever the need arises.
But on RTAW I think for every 10 things you would gift i estimate 3 would end up on the classifieds later, 5 likely died, 1 would disaprear off the planet and maybe 1 would regift if they had similar sucess.
Unfortunetly I havnt seen anybody regift anything ive given them on here (yet, but i am still hopeful), but there has already been an instance of reselling with the person saying "it spit so many times, it went crazy" three weeks after they were given freshly cut frags, that normally take two weeks to heal. Even giving them the benifit of the doubt that this somehow happened, you would generally hope they would share their good fortune in the same light they recived the coral.