Could you please elaborate on the downsides? Gov't has your data since you were born, complete with your photos, IDs, you name it. What makes you think it's any different now?
To imagine it a bit more viscerally, imagine instead that the system had no cameras and instead required you to submit your daily movement report at the end of each day. An agent walks from door to door and you hand him your written report of exactly what you did today and that gets entered into the Government Saftey and Oversight Commission Database. What are they going to use all that data for? There are only a handful of good reasons, but a disproportionate list of bad reasons that explicitly limit freedom.
Second to that. Would you be as comfortable going to a strip club or a fringe political gathering or a conference for a controversial topic if you knew you had to put it in your report? It has a chilling effect on freedom of movement and pushes fringe activities that are perfectly safe and legal into the darkness.
Ubiquitous facial recognition fills in all of this missing data well enough, and without you doing anything but walking out your front door.