Symantec just released a white paper where they compared their product with 6 other enterprise endpoint security products. They had AV-Test do the review, and they included above graph to show the rise in malware over the years. Note, this only goes until 2010 and the growth is exponential, so for this year you are really looking at 80,000,000 or more.
They noted the following: "With the increasing number of threats that is being released and spreading through the Internet these days, the danger of getting infected is increasing as well. A few years back there were new viruses released every few days. This has grown to several thousand new threats per hour." (Emphasis added)
Add to this that it takes an average of 6 hours for antivirus products to get updated with new definitions and URL's that are 'known-bad' and you can see that relying on your anti-virus only gives you a false sense of security. You also need some very good quality security awareness training as an additional security layer.