An advertiser purchasing display advertising through other ad networks can still benefit from using AdWords display ads because:
she can fill in the gaps of niche and mass-marketed sites using AdWords targeting options
the ad can appear multiple times on a page to reinforce the advertiser’s message
the ad will show on all ad networks and will reinforce the advertiser’s message
she can infinitely loop animated image ads
The Google Display Network allows to you connect with customers with a variety of ad formats across the digital universe. This network spans over two million websites that reach over 90% of people on the Internet. It can help you reach people while they’re browsing their favorite websites, showing a friend a YouTube video, checking their Gmail account, or using mobile sites and apps.