I visited it recently, and the entire Lake area has become gentrified. Almost like an entirely new city, with lots of people out at night. And I wasn't too worried about being robbed. Of course, I was robbed at gunpoint just a few years ago walking home from work in Redwood City - so it just goes to show it can happen almost anywhere. Except, of course, Singapore. Gotta be the safest city in the world.
Unless things have improved a lot in the last fifteen years, it's really pretty easy for a tourist inclined to walk between touristy areas in Oakland to wander into an unsafe area. I wouldn't blame that on stupidity, it's not as if the city puts warning signs up.
Maybe you don't know what the feeling is like? I mean, how long have you lived in Oakland? If you grew up in the city with the 3rd highest crime rate in the US, maybe your barometer isn't calibrated the best?