If this works it's pretty much the equivalent of a mandatory state ID on every online interaction. If it doesn't work very well, then it's going to be that, plus the risk of randomly being flagged.
As a society I don't think we have anything to gain from it; it's certainly tech that's put of Pandora's box, but that doesn't mean we shouldn't use all our cultural/legal means to prohibit/control it.
Anyone in their basement could build this today, but it only becomes a problem if that person has control over police and intelligence forces. Which means the potential for good regulation is bigger than with other tech.
Edited to add point about regulation