I've been concerned about the amount of author and commenter information that the REST API exposes by default in 4.7+, and this site is an attempt to illustrate how serious it can be.

Nothing here is new - people have been talking about the privacy implications of Gravatar for nearly a decade, and the amount of data exposed by the REST API has been pretty controversial. I thought that a easy-to-use tool showing just how easy it is to reveal this information would be educational and, hopefully, a little scary.