It's a means of law enforcement being able to collect data on leftist activists presumably connected to anarchist movements, which the US gov't are charging people against like it's WWI again. Someone with 1k followers on left twitter probably has some deep connections, so (in a similar way to the NSA collecting info on people within social networks) they figure out who all the lefties are. This makes it easier if a protestor is caught vandalizing a federal building, which is the reason for the unmarked alphabet pigs kidnapping people (absolutely never touch fed buildings unless you wanna die)