I'm a little fuzzy as to the inner working of the bots in general. Here's a simplistic run down as I see it now. Then again, I can be quite the dunderhead.
1) Intially a server is set up to send out spam for some product by one or a few enterprising individuals.
2) Someone clicks on an ad to order a product.
3) Zing! They're infected and start sending out more spam which is monitored by the C&C machine. This process continues until there are 10,000s of thousands of members (however, members usually refer to people who sign up voluntarily for something or other.)
4) Question. What happens to the orignal product ordered? Does it get shipped. Is it just a ruse to get machine infected? Or both?