When two people become married, they undertake a duty to one another, a legal obligation to support each other. Keep this in mind; this is what makes marriage such a big deal.

After all, there is nothing preventing two people from living together and then separating without any kind of legal intervention, so long as they are not married. 

This happens all the time. It's called "breaking up with your boy/girlfriend." You cry, or get angry, you get over it, and you move on.

Marriage does not work like that. The Commonwealth grants a license, a privilege that allows two people to pay taxes as an individual, kind of like a business partnership. 

In exchange for this license, the two people implicitly agree to support each other; this is more of a promise to the Commonwealth than it is to each other.  The wedding vows are the promises you make to each other-- to have and to hold, in sickness and in health, etc.-- but the license is a promise to the Commonwealth that you will not let your spouse become a ward of the state.

Therefore, when a person becomes married and then refuses to support a dependent spouse, or when a person obtains a divorce, the court can and will step in and enforce that promise to the benefit of the spouse and, indirectly, to the benefit of the Commonwealth.

The court does this by awarding alimony based upon income of the parties and living expenses, among other factors.

However, the law on alimony is somewhat unpredictable. Recently, Governor Deval Patrick signed into law the long-awaited, much anticipated 2011 Alimony Reform Act. The new statute, Massachusetts General Laws, Chapter 208, sections 48-55, goes into effect on March 1, 2012. The new law sets out specific durations for the termination of alimony based upon the length of the marriage and at “full retirement age.”

While the new change adds certainty it creates new questions, especially as to when and how you can modify an existing order or judgment for alimony.