that's cause there are so few people bombing out in the 925 the city's are able to clean it up in about 2 days, and if it is a highly visible spot in a matter of hours.
that being said, these days i see STM crew up a lot, though mainly with markers. NUT seems to do a bit of bombing.
KAO crew gets up here and there, again i see mainly markers.
i do give an extra amount of respect for folks like raskl who bomb places like danville and walnut creek. rich suburbs with lots of bored cops, where graffiti is a big crime. and where the city as a large enough budget to get things buffed a lot fast than concord or pittsburg.
that's just what i've been seeing the places where i go.