The ads covering the whole background of some websites websites are the most outrageous thing I had the pleasure to discover recently after so much time of ad blocking. They are absolutely aggressive to your very soul.
I've long planned a cyberpunk setting where you can sneak past low-level corporate guards by plastering your clothes in ads for competing companies, because their neural interfaces are configured to only let them see their employers adverts.
Every year that plan feels less and less like silly hyperbole.
I found the ads covering all of the foreground to be more annoying, where you even cannot close them, without opening the link. Pity on those who do not know what a adblocker is and have no one to tell them.