From Frederic Filloux

Over the recent years, the advertising community managed to find a new gun to shoot itself in the foot. It's called targeted ads. Everyone has ugly anecdotes about those. Typically, the stories go like this: You do a web search for an item and quickly find it. In the following months you're deluged by ads for the product you bought. The annoyance prompts many to opt for AdBlocking systems – I did (except for sites I'm in charge of), with no regret nor guilt.

To put it mildly, there is room for improvement, here.

Yep. For some reason, even reputable outfits like John Lewis tend to be particularly annoying in this respect.