Combination of risks led to explosion and oil leaks last summer

Click on this link to read a Sarasota Herald Tribune (11-9-10) article about how investigators of last summer's oil spill have not found anyone to blame.  Apparently a series of risks combined to create the perfect storm.  Critics are worried that BP will be let off the hook by the investigation.  Could a disaster this big occur to due to a series of small seemingly uncatastrophic risks piling up in a coincidental way?