Dropping Dox, now known as Doxing, originated in the late 90s in hacker circles as a way of targeting individuals by releasing documents (dox) about their personal information to the web. As many of these hackers who were doxed were criminals, doxing could have a pretty serious effect on them.
Doxing has spread to the rest of the internet and thanks to the ease of use of search engines, is now a common way for a digitally-minded harasser to invade the privacy of someone. Doxing is unfortunately legal, even when it is pretty clearly harassment or stalking.
In the modern world everyone gets doxed, it's better to do it yourself first, but it is even better to have strict compartmentalization. Just one slip up that ties together identities can be enough.