Thanks for the additional info. I was able to check your account on the backend and I'm seeing destinations for Flashtalking, Amazon Advertising, and Google 360. The cookies you are seeing are a result of the ID syncs that we enabled as part of these destinations. At some point in time, when these destinations were set up, these ID syncs were enabled. I can't speak to why you never noticed them before, but these have likely been active for a long time. Without them, your destinations wouldn't work very well.
If you open an incognito browser, visit your page as a new user, and then use the developer tools to look at the 2nd call to ID service (the 2nd call to dpm.demdex.net/id?), you'll see in the response the ID sync URLs that we fire. Id syncs work by our destination iframe calling these URLs, passing them our AAM UUID, and then them doing a 302 redirect back to demdex.net where they pass us their ID. It is possible that these partners updated the actions their servers do and when we make a call to them, they are dropping net new cookies. That's just a guess, though. Point is, these are working as designed and I can't really speak as to why you haven't noticed them before. If you need more information, go ahead and open a ticket with Customer Care and we'll get those questions answered.
