My main problem with the current implementation is that I can't view all my lists at the same time, side by side (so I still use my own quick-and-dirty Python app to do that).
The author's point about being put in lists named "big fat hairy men" is quite valid though, I think the lists should be private (or at least not visible on the listed user's info page).
I wonder what will happen when someone starts listing people as "Criminals"? Is it libel to brand someone with a list? :)
I should think so. Not sure how it works with more or less anonymous accounts though, I guess it's not libel unless it can be linked to a specific person by those reading the list.
Note: I use also tweetdeck that has a similar concept, which I found very useful. Perhaps that is why I liked the lists concept.