Targeted advertising remains an important part of the free web browsing experience, where advertisers' targeting and personalization algorithms together find the most relevant audience for millions of ads every day. However, given the wide use of advertising, this also enables using ads as a vehicle for problematic content, such as scams or clickbait. Recent work that explores people's sentiments toward online ads, and the impacts of these ads on people's online experiences, has found evidence that online ads can indeed be problematic. Further, there is the potential for personalization to aid the delivery of such ads, even when the advertiser targets with low specificity. In this paper, we study Facebook -- one of the internet's largest ad platforms -- and investigate key gaps in our understanding of problematic online advertising: (a) What categories of ads do people find problematic? (b) Are there disparities in the distribution of problematic ads to viewers? and if so, (c) Who is responsible -- advertisers or advertising platforms? To answer these questions, we empirically measure a diverse sample of user experiences with Facebook ads via a 3-month longitudinal panel. We categorize over 32,000 ads collected from this panel ($n=132$); and survey participants' sentiments toward their own ads to identify four categories of problematic ads. Statistically modeling the distribution of problematic ads across demographics, we find that older people and minority groups are especially likely to be shown such ads. Further, given that 22% of problematic ads had no specific targeting from advertisers, we infer that ad delivery algorithms (advertising platforms themselves) played a significant role in the biased distribution of these ads.

翻译：定向广告仍是免费网页浏览体验的重要组成部分，广告商的定向投放与个性化算法每日为数百万条广告精准锁定最相关受众。然而，鉴于广告的广泛使用，这也使得广告可能成为传播问题内容的载体，例如诈骗信息或点击诱饵。近期研究探讨了人们对在线广告的态度及其对用户在线体验的影响，结果证实在线广告确实可能带来问题。此外，个性化技术甚至可能助长这类广告的推送——即便广告商设定的定向精度较低。本文以互联网最大广告平台之一Facebook为研究对象，聚焦当前对问题性在线广告认知中的关键空白：（a）用户认为哪些广告类别存在问题？（b）问题广告在受众群体中的分布是否存在差异？若存在，（c）责任方是广告商还是广告平台？为解答这些问题，我们通过为期三个月的纵向面板研究，对用户接触Facebook广告的多样化体验进行了实证测量。从该面板（n=132）中收集的32,000余条广告被分类整理；通过调查参与者对自身广告的主观感受，我们识别出四类问题广告。针对问题广告在人口统计学特征上的分布建模发现，老年人和少数群体尤其容易接触到此类广告。值得注意的是，22%的问题广告并未来自广告商的定向设置，由此推断广告投放算法（即广告平台本身）在问题广告分布偏向中扮演了重要角色。