It doesn't just break behavioral targeting, it breaks conversion tracking. Most campaigns are run with Cost Per Acquisition (CPA) goals, regardless of how they'

It doesn't just break behavioral targeting, it breaks conversion tracking. Most campaigns are run with Cost Per Acquisition (CPA) goals, regardless of how they're priced (CPM vs CPC, etc). Figuring out actual CPA depends on being able to match up conversions with ads being served. In most cases, campaigns are being run across multiple ad networks, so you can't just look at total conversions and divide by all impressions. The process for doing this relies on being able to set a cookie when the ad is served and read the cookie back on the landing page for the conversion. Taking away the ability to track conversions will set the online advertising industry back significantly, which is why the major opposition to legislation like this comes from advertising companies.