We were hearing during the Snowden era about the abuse of NSA systems like XKeyscore and others through what was termed jokingly LOVEINT. Anything that's built will get abused in some way - sometimes its even best not to build such databases at all.

Here's CNN discussing NSA analyst abuse from 13 years ago:

https://www.cnn.com/2013/09/27/politics/nsa-snooping/

Here's an article from 10 years ago discussing the police doing it:

https://apnews.com/general-news-699236946e3140659fff8a2362e1...