There is a Bart station at 16th and Mission and one of my coworkers told me they saw someone shooting up on the street. I don't know if there is truth to that but the area gives you that not so safe feeling and I have certainly seen people smoking pot on the curb. I'm not against it, but it does say something about what is going on around an area when people think it's cool to light up in broad day light.
It's a very vibrant area and has a great energy to it that I haven't found in 'nicer' areas like Noe Valley. HOT restaurants and cute shops are always opening up. I love living here.