It took awhile, but Bing has finally decided to retire the side rail in search results. According to the official post, as of March 26th, 2018 ads will no longer be served on the sidebar. While this will affect Bing owned and operated sites, it will not affect syndication partners such as Yahoo and AOL.
Google already phased out the side rail back in February 2016. Similar to most companies out there, Bing watched, waited, and conducted testing to determine what impact the removal of the side rail would have on digital advertisers in search results. According to the post, recent tests indicated that a search results layout which excluded the sidebar actually increased clicks for advertisers, specifically for mainline text ads and product ads with a very minimal impact from an impressions standpoint.
While there was a lot of panic from digital marketers when this change first occurred with Google, most digital marketing advertisers have been pleased with the results. Bing is confident that this change will also accomplish the same goal. Bing does encourage advertisers to proactively analyze their campaigns for the next several weeks to better understand the impact on clicks and impressions.