To explain the first part of the title, doubleclick are one of the notorious advertising companies supplying so-called "3rd party cookies" to track your likes and dislikes across the internet, saving your information across multiple websites (those websites, of course, who use their syndicated ads).
By saying "notorious" I have of course prejudiced the conversation, but if they can prove otherwise I'd be happy to retract.
Now to explain the double take..
I bought a laptop today from a well-known UK retailer. A few hours later I was sent (by a friend) an unrelated article hosted on a well known UK newspaper website. Hitting the article, I had to do a double take, because my laptop was being advertised in a prominent banner.
On refreshing the page, my laptop again... nothing else, no ads for probiotic yoghurt or online degrees, just the exact laptop I'd just bought.
"What's the problem?" I hear you ask; "isn't this convenient for you?".
Apart from the fact that the ad server wasn't clever enough to know I'd actually bought the laptop and probably didn't need two of them, these are the kinds of ads which brought about the cookie law which we all hate. These are the people for whom the law is actually created. The law is only for the bad guys.
The fact that the cookie law was introduced to curb these people is bad enough, but the fact that they're getting away with it while us law-abiding citizens are having to ask users for permission to store cookies is also a pain.
Why are their activities bad? Here's a small example: suppose you have legitimately been using your work laptop to look for things you'd rather your boss knew nothing about (like a new job). Then when your boss is in the room, job ads display on every website you visit... it doesn't make for a happy boss. Or suppose you didn't want to tell your parents you were pregnant yet, but baby clothes and pregnancy test ads are displaying when you're doing homework in the lounge..
Do I care enough to report the Guardian website to the information commissioner? Probably not, but undoubtedly they will have to change their policy soon..