Those may each be part of the issue, but I think that a big part of the issue is the actual crime statistics that show that, indeed, Oakland is, in fact, a dangerous place by comparison to those other places.
I mean, there's something about Oakland having a little over 3 times the population but a little under 20 times the number of violent crimes as Concord in 2012 [1].
[1] http://www.sfgate.com/crime/article/Crime-up-in-Oakland-much...
So, do you avoid Oakland or avoid the bad parts of Oakland? I, personally, just avoid the bad parts.
http://www.sfgate.com/opinion/openforum/article/Oakland-sees...
I hear that Concord's gotten worse since, as well, but I don't have a good source for that.
Speaking of which, when I get around to running for mayor of Oakland, I'm going to have only 2 planks:
1) Charging the people of Piedmont $50 to drive out of Piedmont.
2) Divesting "Oakland" of almost all of its real estate, while retaining all of its civic debts, then letting the remnant entity of "Oakland" just go bankrupt.
I think this is going to be a very popular platform!
Because of the correlation between crime and demographics, it might be tempting to publicly call out concerns about high crime neighborhoods as examples of racism, but I still wouldn't check your iPhone on the street at night in Oakland.
~~an Oakland resident
Lots of people on the other side of the hills (Concord, Moraga, Walnut Creek) have this idea that Oakland is a really scary place. I think it's partly racial (because of the higher percentage of African Americans here) and partly a PR issue (the 24/7 news cycle only presents sensational items).
I've lived in the area since 2001. I lived in Berkeley for the 13 years prior. I had more problems with crime there, and I was fairly close to campus. People don't normally think of Berkeley as a high crime place, either.
The most dangerous thing I deal with on a daily basis? Cars and bikes. I always cross the street legally, but both cars and bicycles have issues when it comes to respecting pedestrians. I've even seen a police car not yield for a pregnant woman pushing a stroller in a cross walk! He cruised by her within inches. I was dumbfounded. She was in the middle of a 4 lane (2 each way) road.