It can be hard to continue reading the important article about Nato on your screen when it's garlanded by the stack-heeled ankle boots you were browsing through last night.
It's equally hard to maintain the pathos during an email exchange with your heartbroken friend while the sidebar is shouting about online dating and losing weight. It can feel a little like they're trawling through our subconscious.
So opting out of behavioural advertising is something of a revelation. Using youronlinechoices.com is easy enough. You can choose from a list of ad suppliers that you don't mind receiving, or you can just click the big pink "off" button.
I did this and immediately it felt like surfing the web in 2003, with acres of white space and not any of the targeted marketeering that means I never see ads for cars or power tools. Switching it off via Google itself is surprisingly anticlimactic, perhaps because it's so simple. You can opt out of targeted adverts while searching and browsing and also in your email settings.
You're supposed to be able to choose from a list a categories that you would see and those you'd rather not, but I'm offered nothing other than the stark choice of opting in or opting out.
After each click, there are no fewer ads, of course, it's simply that they're geared less obviously towards me.
Nevertheless, even the generic ads are still unnervingly close to the bone: they're for bank accounts, insurance, digital cameras, holidays and laser eye surgery.
You're fooling yourself if you think they don't apply to you at all.