I love educating people about why there is malware and spam, when a succint article comes along with some good background I love to drop it like it's hot right on our blog.

http://krebsonsecurity.com/2012/02/whos-behind-the-worlds-largest-spam-botnet/

In the summer of 2010, hackers stole and leaked the database for SpamIt andGlavmed, sister programs that paid people to promote fly-by-night online pharmacies. According to that data, the second-most successful affiliate in SpamIt was a member nicknamed “GeRa.” Over a 3-year period, GeRa’s advertisements and those of his referrals resulted in at least 80,000 sales of knockoff pharmaceuticals, brought SpamIt revenues of in excess of $6 million, and earned him and his pals more than $2.7 million.

A variety of data indicate that GeRa is the lead hacker behind Grum, a spam botnet that can send more than 18 billion emails a day and is the primary vehicle for more than a third of all junk email.

What a fun bedtime story to tell the kids.  There is big money in the spam and virus game.

Just to add a little side note to the conversation, many viruses you get don't even give you a symptom, if your computer is part of one of these botnets they want to keep that a secret so you don't go get your computer fixed.  The virus will be entirely hidden, and these guys will spend their 6 million dollars of revenue (in addition to buying cool houses and cars) on making sure their latest virus is undetected so it can remain on your computer stealing and spamming as long as possible.

We usually only see the other type of recent virus, that will display itself front and center and ask you for money to "upgrade" the "Fake Antivirus" they installed on your computer.