There's a fascinating little sidebar article in the Economist (4 August 2007), "Misconceived:"
Now that anonymity is no longer possible, there has been a huge decline in the number willing to donate. So more patients travel for treatment to countries where anonymity is still legal. If this new proposal is implemented, it may give such “fertility tourism” a further boost. It may even compound the problem that it purports to solve and encourage parents to reveal still less.