In September Google announced “Customer Match”, a new tool for advertisers to target their existing customer using their email addresses. “Customer match” is almost like Facebook’s “Custom Audiences” but Google and Facebook seem engaged in “a privacy race to the bottom” and Google may have taken the lead.
Targeting email addresses
Advertisers aim at targeting prospects and existing customers. While remarketing offers them the opportunity to target potential buyer, advertisers were so far not able to differentiate between their existing customers and new prospects. They also lacked the possibility to target their “loyal” clients (i.e. those who have subscribed to a loyalty card) because there is no link between the cookie IDs assigned to their browser by ad-networks and their loyalty card number or even their online customer account. “Custom Audience” and “Customer Match” (thereafter “Customer targeting”) create a bridge between the email addresses used to create a “Best Buy” account or CVS loyalty card and Google and Facebook accounts.
Via “Customer targeting”, advertiser will be able to pull the information they gathered about your shopping habits and leverage it to target you on Facebook and on Google. The advertiser won’t send directly ads that they want to show you and attach it to your address. Instead they will create group of “audiences” by creating groups of email addresses of their customers. They will send those hashed email addresses to Facebook (or Google) which will check to see if those hashed email addresses match those of registered users.
Technically, Facebook does not see the email address but just the hash. So if you’re not in their user database they will not be able to know that you’re a “Best Buy” customer. That being said, the technical guarantee may not be sufficient considering the computational resources of giants like Google and Facebook that could generate many hashes to brute force the hashed email address and retrieve the lists of customers. In fact, in another context Google seems to admit this and required that Google Analytics user don’t send hashed identifier like email addresses or phone numbers.
Therefore the only guarantees are contractual; they are the engagements that Google and Facebook take when they receive email addresses (or phone numbers). Facebook and Google are committed to not retrieving the email addresses of people that are not registered to their services. Similarly their contractual clauses prevents them from keeping those lists of hashed identifiers for more than a week (that would remain largely enough for them to break most of them).
Facebook Terms of Service are quite constraining for Facebook itself as they more or less prohibit Facebook from doing anything with the hashed email addresses other than using them to help an advertiser reach its audience. Therefore, Facebook cannot add information to the profile of its users. In fact Facebook specifically forbid appending “Custom Audience” data to users’ profiles. Furthermore, Facebook won’t let an advertiser target the audience of another advertiser. For instance “Target” should not be capable to target “Best Buy” customers. Facebook adopts a data processor position with respect to Custom Audience, the advertiser being the data controller.
Google Customer Match
Google took another approach with its service. Google did not include clauses to prevent them from appending “Customer Match” data to user’s profiles. The restrictions only impact the list of email addresses , but there is no restrinction on the use of the list of matched profiles which can therefore be used by Google.
Consequences of Google posture
Google’s decision to include “Customer Match” data in its user accounts will impact user’s privacy and also advertiser’s competition.
- Since the data will be included in the account, it means that Google will have a more comprehensive view of its users which is a big step to merge offline and online data (also known as data onboarding). This may have significant negative impact as it puts Google at the center of all these data-flows… until Facebook announces its riposte.
- On the up-side, this could be beneficial for transparency because users could be made aware of the advertisers targeting them if Google shows these data on privacy dashboards (that’s a big if).
- However, because Google is a data controller with respect to ‘Customer Match”, advertisers may be reluctant to share information about their customers knowing that it could potentially be re-used by competitors or by Google itself. Not only Google could share these data with other advertisers, thus allowing competitors to target each others audience to stir-up the demand and thus the price, but Google could also be tempted to use the data for its direct benefit.
Thanks to Armand Heslot for providing feedback on a draft.