@johnnyryan RTB is the protocol (and yes, position data are part of the specifications), but all this tracking is made possible by the people that decided to collect your geo data for money. Basically, you can be sure that all free apps on your phone that have an access to your position WILL send these to advertiser, using RTB protocol. So to solve this problem at core, geo location on a phone should be highly protected (but that is not in Google/Apple interest)