PG&E culture played a part in the San Bruno incident, according to this article in the San Jose Mercury News. "That telling lapse was one of many disturbing signs that the company's culture had turned 'dysfunctional,' according to a five-member expert panel picked by the California Public Utilities Commission to look into the explosion. The panel's report, released Thursday, drew headlines for its suggestion that improperly monitored work on a nearby sewer pipe may have led the San Bruno pipe to rupture."
For a copy of the Commission's report, see here.