[zelphirkalt]

Only that it won't stay at the minimum information. They will want more and more, with some thinly veiled greed for more info.

For example hotels: Some chains may think to advertise using fear mongering, claiming that their hotels are the safest, because they perform background checks based on the information from their customers' ID. You don't want that? Fine! Go elsewhere then! This is private property, if you don't agree to these ToS, you are not allowed to enter or rent rooms, sooo sorry! All you had to do is sign your privacy away here and then let us mine your data ... You don't have anything to hide, do you??

The issue is, that every single involved party from business to government has an incentive to get more data from this system. If there are no laws with guaranteed severe punishments for violations edged into our inalienable human rights and constitutions and those are properly followed up on, in addition to making it technologically impossible to extract more information than necessary, the system sooner or later will be abused.