Be prepared for nontraditional disasters

It sometimes surprises me that many business continuity plans don't look at systemic contingency situations as well as collateral disasters.

The organization's main supplier suddenly goes out of business or has their own disaster and can't provide supplies or service. Collateral damage could include a problem with another structure, but due to structure damage, the on-scene commander (Local Emergency Managere, Police, etc.), they cordon off access to your facility with no specific resolution time or date. Your operations are active, but no one to run or maintain the operations (IT, Call Center, Trading Floor, etc.)
Strategic Planning 101 says that you need to consider all failure modes and contingency events, including those outside your control (competition, regulatory, etc.). We passed the course and could fail the organization.