Honestly, it doesn't really bother me. What's the difference between a facial recognition camera and a couple of police stood on a corner looking for people who match a certain picture or description? And realistically, what are they going to do with the information?
Monitor crime? Fine by me, I'm not committing any and I'd like them to catch those that do.
Use it to advertise to me in a similar vein to internet cookies? Don't really care. I ignore what Facebook tries to sell me and I'm sure I'll ignore that too.
Blackmail me? With what exactly? Being in a public area?
Track my movements? Well they'd quickly become very bored watching my daily commute and besides, my phone already tracks that anyway since it knows (without my telling it) where 'home' and 'work' is.
I'm just not interesting enough for the government to want to watch, and in any case if I was that paranoid about the government watching me I'd have moved to Orkney a long time since!