Economics of Spam

An experiment about spam conversion rate (the rate by which spam emails result in purchases) show that less than 0.00001% of spam emails result in sales. The experiment was performed by infiltrating the storm botnet and sending out spam emails referring to fake sales pages operated by the researchers (I won't comment on whether I consider this method ethically acceptable. At least, no damage is done to the test subjects).
As sending out spam comes with a cost, this low conversion rate poses a problem to the spammers. The authors assume that the retail price for sending out spam is $80/million spam mails. That's not a business because one million emails result in only 0.1 conversions by the conversion rate quoted above.
The conclusion in the cited paper is that the storm botnet is "vertically integrated" and thus operates at lower costs than $80 per million of sent spam emails.
The good news is that spam business seems to operate at the border of profitability. If this is true, then measures that reduce spam profitabiity further might effectively reduce the quantity of spam.