From July 2007 to June 2008, Drupal core was downloaded more than 1.4 million times. The year before, from July 2006 to June 2007, Drupal core was downloaded 620,000 times. The number of downloads doubled in one year's time!
Suppose you get attention through some text you send out over the Internet. Would you want your audience to copy this and pass it on to others who might pay attention in turn?
Now, increasingly, money tracks attention. Those with a great deal of attention can easily obtain money, should they want it. Those with little attention will have a much harder time obtaining money.
[N]ow that "stuff" is so easy for people to get, the real economy is in attention -- the one thing which cannot be commoditized or pirated or open-sourced.
For people new to Drupal, this is more than just a CMS. This is a web platform that you can extend and customise in more depth than any other I have come across. Drupal should be on your shortlist for any new build.