Google has reached an agreement to buy web ad behemoth DoubleClick for $3.1 billion in cash.

If that sounds like a lot of money, consider this: it’s about 1/5th as much as the U.S. Army has paid to Halliburton in no-bid contracts since 2001. I got that information from this website, which also features interesting drawings of how big different amounts of money are. I assume, of course, that their information is accurate.

You may not know DoubleClick, but they know you—likely a lot more about you than you’d like.