"You shall not misuse the name of the LORD your God, for the LORD will not hold anyone guiltless who misuses his name." --Exodus 20:7
What do you think of when you hear this commandment? Do you think of its colloquial statement (drawn from the King James Version), "Don't take the Lord's name in vain"?
What are you used to thinking of, when you think about what this commandment means? Do you think of the swearing of oaths using God's name? Do you think of avoiding God's name in speech altogether or only under specific circumstances? Do you think of certain curse words that place God's name in a vulgar context?
Caution in our speech in this manner can be a good thing if it also schools us towards caution in our thoughts and our hearts. That said, there is, of course, the temptation--as there is with all commandments and precepts--to take the law only in this sense: that if we don't use God's name in oaths, or we don't mention Him in expressions such as "Oh my God," or whatever may be appropriate to our culture or denomination, then we're doing all we need to do.
I would like to suggest that there's far more to it than literally suggesting when we may or may not use the word "God." What about when we try to claim God as our justification for our own selfish and hateful acts? What happens when we use God, for instance, as an excuse to belittle people, to cheat them, or even to commit acts of violence? I'm not looking at just the "obvious" abuses that we see in the history books--I'm talking about even the simple things, treating those with different beliefs inside and outside of our faith, with the sort of coolness we would not think of doling out to those who are more like ourselves. If we do these sorts of things and then claim God wants us to do that, what we are doing is ascribing to Him a false motive...our own sinful motive, that is.
In essence, what we have committed is defamation of character against our Lord, by the "witness" of our words and actions.
Caution with our choice of words is a good thing--but if we become legalistically fixated on only the use of this phrase or that, we, like the Pharisees before us, may risk missing the real elephant in the room, and the spirit within us that this commandment was intended to root out.