The gas main was put in in 1938, when the area was completely undeveloped. The housing development went in 20 years later -- making the builders the geniuses of whom you speak. But on the San Francisco peninsula, there isn't really a lot of undeveloped land except steep mountainsides, so that development was pretty much inevitable.

Also, though nothing is certain yet, we are hearing that there were complaints of the smell of gas and investigatory visits by PG&E going on for a couple of weeks before the explosion. So perhaps those geniuses will end up bearing some responsibility, eh?