I won't ever sell your information to anyone. If you give it to me I use it only to contact you back if you have contacted me.
Also, I use Google Analytics and have the following Google tracking technologies turned on:
Remarketing, Google Display Network Impression Reporting, the DoubleClick Campaign Manager integration, or Google Analytics Demographics and Interest Reporting.
Visitors can opt-out of Google Analytics for Display Advertising and customize Google Display Network ads using the Ads Settings.
I will not facilitate the merging of personally-identifiable information with non-personally identifiable information previously collected from Display Advertising features that is based on the DoubleClick cookie unless I have robust notice of, and the your prior affirmative (i.e., opt-in) consent to, that merger.
I also respect the opt-out header.
Basically, I track this stuff so I can learn how it works and then provide my clients with some form of insight.