Does a tree know oil is $100?

Does a bird know it is 2008, or what day it is... what day does your dog think it is? Are you any much older at 30, than you were at 29?

Oil reached an historic $100 a barrel for five reasons over a long period of time

Supply
We can't pump enough to meet the perceived demand. Most models suggest that world oil supplies will peak around 2010, while world population will continues to balloon.
Demand
North American has always been a large consumer of oil, however, we have been preaching the gospel of Capitalism to far away markets like China and India so that we can expand markets for cars and refrigerators.... To live like us they must consume like us. People living with simple means have been taught that they need to consume.
Sagging dollar
The value of the dollar has been falling which may sound great for exporting, but for oil producing countries, it means that they get paid less. There is an incentive to keep the price high right now by foreign producers.
Scary stuff
People fear supply cuts due to global unrest and how government manages fear. Real or perceived, fear makes a good investment in oil more valuable
It's a great investment
As much as people would like to blame big oil companies and commodity traders. There is a good possibility that your 401-K or pension is partially invested in oil because it has been such a good speculation. Speculation of profit builds profit and price.

We can't do much about supply or global events, but we can control consumption and place our fears and investment practices in perspective. One hundred is just a number; to fear it only makes the price higher.