There are actually two alternatives.  

One is that the contract was, unwittingly, not legal in the first place, and both parties bear responsibility for not doing enough due diligence to realize this.  Giga is now, having done the due diligence, executing his obligations in the nearest possible manner consistent with the law.  Since this thread right now is really about dividend payment rather than the fact that it was an exchange security, this alternative isn't super relevant to the current debate. But it still fits the situation as you describe it.

The other alternative, which is more relevant right now, is this.  GLBSE was not legal before in terms of its dividend payment processing system because it did not collect all the information it should have and did not issue the proper tax documentation.  Now, Giga is taking over this processing functionality, which used to be GLBSE's responsibility, and he is doing it differently than GLBSE did in order to be legal.  You are mad at Giga because you are now having to provide more information than you did before.  

But your anger is misplaced. The difference that you are experiencing does not stem from Giga changing his mind about what what he wants from you.  The difference stems from the fact that you are moving from one payment processor to another.  Your old payment processor, GLBSE, apparently didn't ask you for the right things.  Your new payment processor, who happens go be Giga himself but could just as easily be a different exchange or processing contractor, is now asking you for the right things.

If you want to be mad at somebody, be mad at GLBSE for making you think in the first place that you could receive these kinds of payments without supplying tax information.