Break-Ins?

Since my move to the Bay Area, not only have I experienced a home break-in myself, but I've heard of four other recent situations in a varying degree of neighborhoods where people have had either their home or their car broken into. Is this a common phenomenon here? Is it a symptom of a high population density in an affluent area condensed with a number of poor neighborhoods? Or perhaps a sign of the economy?

Either way, it seems strange, considering I've never heard of such a high number of breakins before moving here...