Why are viruses written?

Mikko Hypp?nen discusses the various motives of Crimeware in a follow up to Re:solution.

Why are viruses written?

This is a 10 minute YouTube video that I found interesting even though it is a bit of a commercial for their anti virus application:

This is the second informative video I've seen put out by F-secure.

I found it interesting,too. Good wide-view sort of round up of where the malware writers are at at the time of making. Quite eye-opening.

I would bet the average user who happens to be hosting part of a botnet wouldn't have the foggiest idea that the resultant profits are supporting insurgents in places like Iraq.