Seth Godin thinks the general web population isn't savvy enough to clear cookies. I think he's forgotten one thing, though. (And this one thing was pointed out in my most recent Self-Deception Series article.)
In order to keep a Wintel machine running, it has become necessary to learn how to use spyware removal and maintenance utilities. And guess what these utilities identify as spyware? Adserver cookies.
I can't speak for Jupiter, but perhaps they're not talking about the run-of-the-mill clear-out-your-cookies.txt-file type of cookie clearing. Perhaps they're also referring to the usage of utilities that do that for web users. Those could include anti-spyware utilities and privacy software like Window Washer, Privacy Guardian and all that kind of stuff.