  Programmatic advertising consists in automated auctioning of digital ad
space. Every time a user requests a web page, placeholders on the page are
populated with ads from the highest-bidding advertisers. The bids are typically
based on information about the user, and to an increasing extent, on
information about the surrounding media context. The growing interest in
contextual advertising is in part a counterreaction to the current dependency
on personal data, which is problematic from legal and ethical standpoints. The
transition is further accelerated by developments in Artificial Intelligence
(AI), which allow for a deeper semantic understanding of context and, by
extension, more effective ad placement. In this article, we begin by
identifying context factors that have been shown in previous research to
positively influence how ads are received. We then continue to discuss
applications of AI in contextual advertising, where it adds value by, e.g.,
extracting high-level information about media context and optimising bidding
strategies. However, left unchecked, these new practices can lead to unfair ad
delivery and manipulative use of context. We summarize these and other concerns
for consumers, publishers and advertisers in an implication analysis.
