I've worked on a number of applications, where we need to make a decision as to what the long/lat will be of "Unknown" - and we always pick something that is guaranteed to throw a flag for downstream consuming applications.

Recognizing how your data will be used, and taking some precaution to ensure that it doesn't result in scenarios described in the article is quite often fairly straightforward. (As evidences - The article itself made it clear that when they don't know the actual location, they have changed the long/lat to return a value in the middle of a lake to avoid this sort of problem in the future).