Support Scams Part Umpteen

UK journalist Kevin Townsend has blogged today on what sounds like two support scam phone-calls of a type I've mentioned here a few times since a colleague at another company drew my attention to it last month.
Interestingly, while one story sounds like a classic "you have a virus" call, the other is a "your computer is running slow" call. Now that sounds bizarre to me. There are circumstances under which a third party might conceivably get a notification that a PC at a given IP address (say) is behaving suspiciously like a zombie (for example), though those circumstances are far likelier to arise in a corporate context than at home, because of the use of dynamic addressing and shared gateways. To believe that your PC is broadcasting the fact that it's running slow to a third party requires a greater leap of faith (that's a polite way of saying gullibility) on the part of the customer.
Here's a thought that's been troubling me since I saw that blog, though. So far, all the instances I've heard of have claimed some form of affiliation with Microsoft or Cisco, or at least to have support technicians with appropriate certifications approved by Microsoft or Cisco.
However, one of the ideas around at the moment is that ISPs might (or even should) regulate customers whose systems are compromised by malware (continue reading...)