@Wizofoz
The text provided by sleeve of wizard is exactly what I have seen in the Flight Handbook of every Boeing aircraft capable of dumping fuel.
Sure, design has moved on, but common sense is not a common virtue. I would be extremely ticked at the guy who dumped fuel onto me (even if the manuals allowed it). Also, while I think the odds are quite low that a stray lightning bolt will set you ablaze, it's not something I plan on testing, unless I'm already on fire and need to land ASAP. That being said, don't forget, landing overweight is always an option if the situation warrants it.