but I saw this mentioned at their web site when i was researching DNT+ whether a FAQ or something else I can't remember.
But 'if I remember rightly' this is the strategy they use to prevent web site cookies from tracking back on us. The cookies are "No follow" cookies so I just assumed they were the web sites' own tracking cookies modified in some way.
But like I say, I may be wrong.
I think I found it. In their Support > FAQ > "More questions" page; http://www.donottrackplus.com/faqs2.php
Why do I see more cookies added to my browser?
Those cookies are what we call opt-out cookies. They protect you from targeted advertising because when these cookies are in place, websites are unable to put their own trackers. They signal to advertisers that you want to opt-out of receiving target advertising (it's like the "Do Not Call" list for targeted advertising). While regular cookies tell websites information about your online behavior, opt-out cookies tell advertising companies that you *don't want* to receive targeted advertising. They're the same cookies for everybody, so they can't be used to track you, and we keep them from getting deleted to ensure maximum opt-outs.
Please see this page for more info: http://abine.com/optout/