For some background on the topic of the universal property ID (UPID), read Rob’s post as well as Michael Wurzer’s post that Rob responded to.

First, let me be clear: I 100% agree there is value to be had with a universal identifier of properties. Not having such a system results in a number of inefficiencies between industry (and non industry) parties who own and use property data in some capacity.

That said, I do want to call out the long term risk, and likely result of such a system. It will be much easier for people to match and sell user and property data across datasets.

This has already played out with Facebook, which became the de-facto ID number for “people” over the last decade since everyone had a Facebook account, and they had so many APIs that allowed any partner website/app to pull from. In April of this year when they migrated from Graph 1.0 to 2.0, Facebook began returning unique IDs — PER authenticated app. It’s an issue we had to battle while building Horizon. I wrote in the post:

I have a theory (no proof of this) as to the reason Facebook made the change. They said publicly it was for user privacy reasons; I don’t buy that as the core driver. I believe the real reason is they want to be at the center of the data sales pipe. With Facebook graph 1.0, every user had a unique identifier across all apps. This meant that “App A” could match data associated with Facebook id #12345 with data from “App B” for that same user. With Facebook graph 2.0, every user has a unique identifier for each and every single app they use. Your unique id for “App A” may be 12345, but your id for “App B” is 456789. My belief is a massive number of sites/apps/companies were selling individual user data matched on Facebook id number (think of how many failed startups probably sold their data assets without your authorization). That will not be nearly as easy of a matching mechanism now that those id numbers are only unique across a single app — and hence it will be exponentially easier for Facebook to monetize all that data themselves because they are the only ones who can match data across numerous different apps.

I believe the same thing will eventually happen with a universal property ID. If a UPID is tied to a corporation, whether that be Zillow or Realtor.com or RPR or someone else, eventually they will likely want to reel in the openness with a new identification number structure — same as Facebook did this year. Sure, UPID increases efficiency for many for legitimate business purposes with clear user approval — but it also makes it exponentially easier for user & property data to be sold and matched across various web and mobile apps. You can bet an individuals address, or UPID if it were to exist, is part of the data being sold on the black market every single day.

Does the good outweigh the bad?

You tell me.