I guess that I'm in the minority in the part of the blogosphere I read in that I believe the Massachusetts high court overstepped its authority. The decision about whether to allow same-sex couples to marry is one that should be left to the people's representatives in the state legislatures, not an unelected court. It seems to me that the advocates of gay marriage are using the courts (in the same way the political left does on other issues like abortion) to impose on an unwilling majority a change in the definition of the fairly basic institution - marriage.
Not being neither a debater nor a philosopher, political scientist nor lawyer, I'm probably going to say this badly. It seems to me that law is the tool used to describe the formal structure of a society; i.e. what types of conduct are acceptable, what methods are to be used to resolve disputes, etc. . A written constitution serves as the base of the structure, and the rest of it built via the creation of laws compatible with that constitution by the people's elected representatives (the legislature). The job of the courts is to apply existing law to settle the inevitable disputes between individual citizens, citizens and the government, etc. . It is not the job of the courts to write the law, and this is where I believe the Massachusetts court went astray.
As far as I know, it is implicit in the definition of marriage (at least in any culture that I've heard of) that it involves a couple composed of one member of each sex. Changing that definition is not a modest step, and in a society that is a democratic one this kind of change should occur via democratic processes - in other words, by persuading a majority that redefining marriage to included gay couples is the right thing to do. In this case getting a court to impose this change by judicial fiat as wrong and undemocratic. Gay folks were not without a voice, and can over time convince the majority and gain more acceptance for the idea. In the meantime the court's action may boomerang, since a lot of people are not amenable to this sort of thing being shoved down their throats. If nothing else, the folks who oppose gay marriage may gain support from people who believe the courts too often step on the rights of the majority by dictating law to the legislature. The justices should have left this one alone.