I got this off of boingboing.net: "I [Raymond Chen, Microsoft] have kept every single piece of spam and virus email since mid-1997. Occasionally, it comes in handy, for example, to add naïve Bayesian spam filter to my custom-written email filter. And occasionally I use it to build a chart of spam and virus email.
The following chart plots every single piece of spam and virus email that arrived at my work email address since April 1997. Blue dots are spam and red dots are email viruses. The horizontal axis is time, and the vertical axis is size of mail (on a logarithmic scale). Darker dots represent more messages. (Messages larger than 1MB have been treated as if they were 1MB.) Note that this chart is not scientific. Only mail which makes it past the corporate spam and virus filters show up on the chart. Why does so much spam and virus mail get through the filters? Because corporate mail filters cannot take the risk of accidentally classifying valid business email as spam. Consequently, the filters have to make sure to remove something only if they has extremely high confidence that the message is unwanted. Okay, enough dawdling. Let's see the chart. " http://weblogs.asp.net/oldnewthing/archive/2004/09/16/230388.aspx