But a lack of transparency means those biases are hard to spot and still harder to regulate.
From July, Google won’t sell search ads for payday lenders, adding such loans to a list of banned products that includes guns and explosives.
Separately, Facebook has been forced to rebut reports of bias in its trending topics feature.
Opinion is divided on whether the two developments are on the same spectrum, and whether there’s a wider question of "Quis custodiet ipsos custodes?" (Who guards the guards themselves?).
Google’s decision is more clear cut than Facebook’s, Martin Harrison, head of strategy at Huge, says.
"Any experience provider has a duty to protect its users from harm," he says. "Google clearly believes payday loans are harmful, and that payday-loan advertising on Google is par-ticularly good at facilitating that harm. So it feels like the right thing to do."
Making sure people have access to different points of view is more complicated, Harrison adds. "The harm is less clear and the solutions are harder."
Digby Lewis, head of platforms and distribution at Iris, says it’s naïve to assume tech companies are dumb pipes for content. "Somehow, because tech firms represent a futuristic world where machines can do everything we can, we consume our news feed without a second thought for a hidden agenda," he says. "Algorithms are written by humans – and humans have agendas."
The basis on which the two companies make decisions to publish, or not publish, content is unclear. The internet is borderless, meaning there is no global body that can realistically act as a watchdog.
Kenny Jacobs, chief marketing officer at Ryanair, is fighting his own battle with Google to remove search ads from eDreams. Ads from the online operator appear top when a user searches for "Ryanair" and "easyJet".
Too often, Jacobs says, the two media giants hide behind the excuse of tech: "I’m a big fan of Google’s, but the attitude is ‘It’s the algorithm, not us’, and Facebook says the same thing. They point to the algorithm like it’s the Wizard of Oz and there’s nothing they can do about it."
Lewis thinks it might be time for a "global internet ombudsman" – and a little more scepticism: "Perhaps we shouldn’t trust everything we read on the internet."