The new Flexible Reach setting gives advertisers more control over where their ads appear and who sees them by allowing advertisers the ability to choose multiple targeting options now at the Ad Group level instead of the Campaign Level.
I just noticed the new feature in a client account yesterday under Campaign SETTINGS; Networks.
Previously with campaign level settings one targeting method was available per ad group with the Broad Reach setting, and the Specific Reach setting ads only show when criteria matches all the targeting methods. This caused management difficulties for advertisers as a campaign level setting. I often found myself segmenting ad groups out new campaigns to allow for more targeting freedom. With Flexible Reach you can choose multiple targeting methods within one ad group and modify bids or targeting methods as you wish for easier management and better performance.
Advertisers can begin to move their campaigns to the ad group level targeting by visiting their SETTINGS tab but be warned that once you change to Flexible Reach you can not revert back to the previous setup.
Once your campaign has Flexible reach enabled all new ad groups to the campaign will start using the new settings.
Over the next few months Google plans to move all campaign that target the Google Display Network to the new ad group level Flexible Reach settings. I hope this is the beginning of a move to bring some campaign level settings down to the ad group level.