kopakabana
In which sense?
And other companies getting referrals can’t connect the dots when they know the user clicking on the AdWords Ad and what the Ad was for?
Companies that work with big data companies run AdWords campaigns in Google for other companies, right?
Even if Google isn’t evil and does everything in the interest of privacy, if their ads, based on your preferences from your emails and browsing history, are used to direct you to some product, there is a way that other companies will learn of those preferences, store them, sell them, and use them.
They might be able to get you a helicopter ride to NORAD, so you can stop it.
Those who will use your info legitimately will probably use an API, but those who only want your data can hide their IP across a number of cloud agents to extract all of the data from your site regardless of whether you offer an API or not unless you use CAPTCHA.