This change seems like it will have the unintended consequence of transferring more power into the hands of large advertisers. For one, this breaks company's (

This change seems like it will have the unintended consequence of transferring more power into the hands of large advertisers. For one, this breaks company's (advertiser's and 3rd party data aggregator's) ability to link customers to campaigns, which effectively pushes measurement back to the advertising platform who have an inherent conflict of interest. They are selling the ads, and telling you how efficient the ads are. Additionally, the only companies that can do battle with Apple to find loopholes/engineering solutions to this change are the companies that are (a) very large, (b) have the resources and talent to throw at the problem. There are several third party data providers that are basically toast now. Edit: I don't work for FB, but I do build ML lifetime values models, which will get much harder after this change is made.