Winston Crawford, the head of iAd Marketplaces, has left Apple to join a startup.

That startup, Drawbridge, is dedicated to tracking people as they switch devices and as they go from online to in-store purchases. iAd was launched as way to help developers make money on free apps and will soon be used to help publishers make money on the new iOS 9 News app. So why to Crawford have to leave to go deeper into customer tracking?The Wall Street Journal:

[Apple] has been unwilling to push the envelope in how much data it will share with advertisers.

"I don't believe they are interested in this capability because they have a strict policy around what they do with user data," Crawford said. "IAd has great assets and great capabilities, but they are going to follow Apple's policy to the letter of the law."

Apple has been making privacy and security top level priorities, and positioning them as key differentiators, for a while now. How Apple reconciles that with iAd has been the subject of some debate.

The company has long refused to automatically opt customers into traditional data collection pools, like demographic information. That's led to media and other industries expressing very public levels of frustration.

Apple has also refused to engage in other, now common, forms of data analysis and brokerage. So much so, apparently that executives interested in doing things like tracking people across devices, and between online and in-store, feel like they have to leave Apple and go do it elsewhere.

Measuring the effectiveness of mobile advertising is challenging because people may browse for products on their phone and make purchases on their PC. In this field, Drawbridge competes with Google and Facebook, which offer advertisers the ability to target ads to logged-in users on multiple devices.