There are a wide range of ad extensions an advertiser can use to improve the performance of a pay per click search advert. One such ad extension that has been available for use since its launch in 2013 was the review extension. This was an ad extension which allowed a quote from another website (the reviewer) to display below the description of the search advert, providing feedback, more information or a review of the business and its advert. However, as of January 2018, Google are looking to remove the review ad extension, with the ad extension completed deleted from February 2018 onwards.
 
In an official blog post from Google, they state:

Review extensions will no longer show with ads starting January 2018.

In February 2018, review extensions will be deleted along with their performance data. To save this data, download an extensions report by going to Extensions on the Ads & extensions page in AdWords. If you’d like to continue showing more information with your ads, we recommend using sitelinks, callouts and structured snippets extensions.

What does this mean for advertisers?

If you have any PPC campaigns that use the review ad extension, you should start to look to remove it from your PPC campaign and replace it with another relevant ad extension.
Although Google states the review ad extension can sometimes improve the click through rate (CTR) of an advert by up to 10%, the effect of the removal of it should not be too severe, considering the review ad extension only appear for desktop adverts and not mobile or tablet ads.
It is an interesting approach, by Google, to remove the review ad extension from PPC. The whole idea behind the review extension is to ‘let customers know that a respected third-party source agrees’, to give the web user more reasons to click onto your advert.
Everything Google does usually has quantifiable data behind their decision, especially for PPC. For this reason, it would not be surprising to know that, overall, the review ad extension was not as successful as others, and therefore was better to concentrate the efforts of advertisers into using more successful ad extensions. On top of this, 2017 was a year of ‘fake news’ – maybe it took much time of Google to decipher through reviews to make sure they are legitimate 3rd party reviews.
I think the fact reviews only appeared for desktop played a big role for the removal of the ad extension. The future of PPC and the internet is in mobile devices. For this reason, having ad extensions that are universally applicable for use over all devices is something Google would want to prioritize.