> Payment in kind: You offer a free service or tool, in exchange for data or data tracking. Example: Foursquare’s free SDKs for mobile app developers, which enable Foursquare to track mobile user location.

This is not payment in kind. This is bribery. App developers are bribed to abuse their users' privacy and personal security.

> Data exhaust: You collect or generate data as a by-product of your core business. ... email managers and personal finance tools all have visibility into consumer transactions; some of them use this to build data products.

Apparently ethics, morals, scruples, etc. are not worth even considering, from this author's perspective.