Display advertising - showing graphical, often interactive, advertisements (ads) on regular web pages - is approximately a $24 billion business . In the simplest form of display advertising an advertiser purchases ad impressions on a publisher’s web page. An ad impression occurs each time a user loads the publisher’s web page and sees the advertiser’s ad as part of the page. To assess the success of display advertising campaigns, advertisers need metrics to estimate the user response. One such metric is the search lift, i.e., the ratio of the proportions of search queries related to a campaign submitted by users who were exposed as opposed to users who were not exposed to the campaign ads. Apart from direct user response, advertisers also expect their campaigns to impact users through social influence. That is, a user who is exposed to the campaign may make other users who were not directly exposed interested in the advertised products, e.g., through word-of-mouth spreading of the ad message. Thus, to get a full picture one needs to measure the response of exposed users as well as the response of friends of the exposed users.