Is there any point in asking?  Some random person will just step up and put forth a vanishingly unlikely theory and rest his case.  Here, I'll save you some time:  hyper-evolved ants gnawed through the wires outside your house, converted the electrical signal to chemical, hot-footed it back to the queen, who then sent you spam.  It couldn't be that someone took a hundred bucks in exchange for 500,000 of verified valid email addresses, I mean, that'd be unthinkable.
http://www.google.com/search?sourceid=navclient&aq=t&ie=UTF-8&rls=GGLJ,GGLJ:2006-52,GGLJ:en&q=buy+lists+email+addresses

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