While I may personally believe that there is nothing wrong with gay marriage, I do have to agree with the initial statements in the California Supreme Court decision, presented here at The Volokh Conspiracy, that declares the marriages conducted this year in San Francisco void. The arguments pertain to the mayor's actions in disregarding state law that marriage licenses shall only be issued to heterosexual couples. The examples given by the court illustrate how the methods used by the mayor could be applied to a wide range of issues in a piece meal manner.
I am not one of those people who complain loudly about "activist courts". If anything, the justices in this case have limited the authority to decide issues of constitutionality to the courts. Say what you will about the courts, but if what they are abusing their authority by legislating through constitutionality, then it can not be a bad thing that that ability has been denied to larger swaths of government.