The silent treatment in any form (from a spouse, coworker, or friend) really stinks. First, it makes you question your relationship and what you might have done, which is an exhausting experience. It's so much easier when people are direct with one another.
But life doesn't work out that way, and people sometimes have a hard time telling someone else that they're upset. While the silent treatment is not the optimal way to handle things, it also doesn't always mean that there is a problem. I talk more about the silent treatment here and what you can do about it.