Two examples of disaster recovery plans going bad:

- my former employer had a small office in Wall Street and then came 9/11. Nothing happened to office, but lower Manhattan was closed. Company had DR plan and there was DR site in somewhere Jersey but when people got there, it was already taken by some other company. Plan B was to fly employees to headquarters but all flights were grounded

- other former employer, after hurricane Vilma in Miami, DR worked, generators started and services were up and running but then people realized nobody can deliver diesel. Luckily company didn't run out of diesel, electricity came back just when there were only fumes left in diesel tank

- current employer has DR site somewhere in north and asking them how long companies typically stay there after disaster, their answer, they still have New Orleans area companies operating there, since hurricane Katrina.