This is most likely a dial up, or DSL connection. Send the complaint to abuse@comcast.net. My experience with this indicates that people frequently receive trial subscriptions solely for the purpose of originating spam. Recently, a wireless spot in a hotel was used to originate spam.
Text based spam is bad enough, but when it includes viruses and trojans, the problem is compounded. CNN suggested this current virus could cost over $250M.
Open Relays pose a problem, as do trial subscriptions, and temporary email accounts. Even though fewer open relays exist in the US, the emergence in 3rd world countries will only increase this problem.
The real challenge is that the existing email protocol cannot authenticate who really sent the email. The advocates for updating the protocol are dwarfed by the advocates for keeping the existing protocol due to the anticipated cost for making the change. Existing applications are based on the current protocol and they would have to be changed.
The CAN-SPAM Act fails because it requires you to identify who sent you the spam. When it comes from a 3rd world country, that will not happen. When the spammers spoof the headers, again you cannot identify who sent the email.