If you want more details, sanfrancisco.crimespotting.org has them, or you can download the raw data from datasf.org. The hot spot at 16th Street BART is drug dealers and in practice there is no reason not to go there.
I would say the off streets right near the 16th street bart are pretty sketchy. I've seen lots of tweakers and crackheads fighting on Hoff and Capp. A crazy guy smacked me in the head "hit and run" style over there, and a roommate was mugged by 3 guys waiting for him in a car.
I'm going to have to disagree. Its accessibility via the muni and the bart, combined with the proximity to the hard-drug areas of town means that there are a number of quick and dirty smash-n-grab robberies of transient ne'er-do-wells. Admittedly I'm biased because I experienced a single one of those datapoints first-hand.
OK, I shouldn't have dismissed it so quickly... there are some real issues there too. But I have spent a lot of time there without worrying about my safety.
