It seems everyone knows everything better than I do. What do I know?
Someone commented that the blog about Cookie Stuffing is really about cloaking and that dear Google is innocent of any wrong doing as they are not responsible for content of advertisements. By that logic, Website owners should not be penalized for external broken links, since we can't check each link, and we shouldn't be penalized for backlinks from shady link farms, since we aren't responsible for what other people put on their websites.
But Google DOES hold us responsible for these things and Google IS responsible for the ads they run. They have to be.
And the company that advertises the scripts says it is doing Cookie Stuffing (not cloaking) and says they are doing Black Hat SEO. Maybe they don't know what they are doing.
By the way, last year Yahoo! was caught cloaking in their automobile ads (see http://www.agerhart.com/seo-rankings/yahoo-caught-cloaking-will-they-ban-themselves/ ). If what the search engine spider sees is not what the user sees and what happens is not what the user intended, it is cloaking, not matter how or why it is done.
Cookie Stuffing usally has to include some cloaking mechanism (or call it something else - it does the same thing) to ensure that the search engine sees an innocent page, but the user gets to the advertiser's page - even if the user doesn't know they got there.