Nick Heer, on Google and Facbook’s ability to associate offline purchases with online advertising views:
For this to be effective, there has to be some association made between a purchaser, whether they have seen an ad, and how that campaign was delivered — through social media, a general website, and so forth. Therefore, there must be enough information to correlate the three factors, which is enough information for specific purchases to be tracked back to an individual. If there isn’t that level of granularity, the service is pointless, isn’t it? […]
When Apple launched Apple Pay, they made a point of stating that they don’t track transactions over time. I don’t think Apple’s privacy protections necessarily prevent Google and Facebook from associating purchases with ad views, but it can’t hurt to consider using services from companies that build privacy protections into their products and services, instead of those that try to find the thinnest tightrope they can walk between what is and is not considered creepy.