Facebook has started placing ads within its news feed, meaning they now show up next to social updates from your friends.

The ads can only feature in a user’s news feed if they or a friend have already ‘liked’ the brand.

Although they are essentially the same as the Sponsored Stories (which already appear on the right-hand side of the screen), Facebook has labelled the new ads as ‘featured’ rather than as ads.

It is a subtle difference, but one that is presumably designed to make it less obvious that the content is actually a paid-for ad.

It only becomes clear that the content is an ad if you hover over the ‘Featured’ text at the bottom of the story, when a text box reveals it is sponsored content.

Facebook said that it was using the term ‘featured’ because it wanted to make it clear to people that they were seeing content from a page or person they had chosen to connect to.

It has also clarified that since people can see marketing messages from both pages they have and have not ‘liked’ elsewhere on Facebook, it wanted to ensure that marketers can only pay for stories to be featured in a news feed if a person has explicitly ‘liked’ the page.

Facebook realises that this will be a contentious issue for some users – they are, after all, placing ads in the only part of the site that had remained ‘pure’ – and as such the ads will appear at a rate of just one per day.

This also suggests that the ads will be positioned as premium content, like Twitter’s promoted slots, so brands will probably have to pay a high price.

That said, as the ads will come from brands you have already chosen to interact with by ‘liking’ them, it may not annoy users too much if they see one additional update per day. That’s assuming Facebook sticks to its promise in the long run.

Either way, a user can always avoid the ads simply by limiting the number of pages they ‘like’ in the first place.