Well, there's Team Rocket. The police force isn't exactly effective about them. And they're managing to get a leg up on the gym leaders now. Bowser outed himself as Team Rocket already, but most people keep that side of their life quiet.

But... that's the thing. Your Gear's ID is tied into the device so you and maskless you will be pretty easy to connect. Well, until you get a second gear. And if you wear the mask all the time that'll be like a new face, one they can recognize over the network and such?

But other than Team Rocket things aren't really that crimey. Some Pokemon thieves, some muggers and pickpockets, a few arsons but some of them are accidental. The police force usually focuses on rather petty things like leaving town while you're under contract to a job.