Yeah, I'm pretty sure this is one of the use-cases lots of people've thought up for location services + AR, over the last decade-plus. It has the following pro

Yeah, I'm pretty sure this is one of the use-cases lots of people've thought up for location services + AR, over the last decade-plus. It has the following problems: 1) A bad chicken/egg critical-mass problem for adoption. (Apple, Google, and maybe Facebook are best positioned to overcome this, if they built the feature in to their OS or apps) 2) Content moderation. 3) Even if you treat it as a friends-and-family thing rather than a more broadly social experience (which solves #1 and #2 fairly well) AR on a screened device is approximately 1,000x worse to use than on the hypothetical non-dorky and practically-useful-battery-life AR glasses that every major tech company seems to expect in our nearish future (judging by their continued emphasis on AR, despite its being kind-of a shit and gimmicky interface outside some niche uses on current hardware) I suspect 2 and 3 are why FB, Google, or Apple haven't taken on the challenge in 1, yet. I expect they will if/when 3 gets solved, and this kind of real-world commenting/tagging thing will be widespread in a hurry.