In the United States, our laws currently protect all egg donors and sperm donors with anonymity. People looking for donors for their future child(ren) look through a list of the donors that identifies them solely by characteristics that could be pertinent to the future parents.
In Australia, however, legislation is being looked over at this time which, if passed, would give more rights to the conceived child. At the age of 18 a donor-conceived individual would be allowed to identify their donor if they wished to, much like American laws for adopted children. On the other hand, donors would not be allowed to find their offspring. Separate rules would have to be put in place to deal with the situation regarding siblings and half-siblings as well. It is quite feasible that a donor would become the donor parent to more than one child, possibly from different families, and if they had their own offspring as well, all of those children would be biological half-siblings at least.
Everything is yet to be finalized as far as the laws regarding egg donation and sperm donation in Australia, but the situation certainly raises a number of opinions and ideas for discussion.