What can Google's Ngram viewer tell us about our society?

Google has recently released a free web-app called Books Ngram Viewer that lets anyone view a graph of how frequently a word/phrase has appeared in books each year going back hundreds of years. Here’s an article from TIME that gives more background about it.

What can this technology tell us about our culture? Is it an effective measure of what our society is concerned with over time? Have you discovered anything cool using it?

When I search for God, there’s an interesting pattern with a gradual decline over the years, followed by a recent upswing in popularity. apocalypse has a huge surge that builds up to right before 2000, and then begins to sharply drop off after. liberties has dramatically declined over time since the 1800’s. nigger is particularly interesting because there are several distinct peaks and valleys.

I’m curious to hear what your thoughts about the Ngram Viewer are, and discoveries you have made.