Turns out, according to BBC, the Register and the US Secret Service, that's not really the case - providing your bank account number is mostly just an identifier that you're a "live one". What the actual game plan is - after getting you to wire them as much money as possible before hand - is to get you to actually TRAVEL TO THEM, after which you can be kidnapped / ransomed / forced to completely empty your bank account in person.
Holy shit. That makes it a little more understandable why the 419 spammer busted by a Dublin sysadmin actually tried to eat his fucking USB drive when the cops showed up. A bit more was at stake than just "you sent some email that people didn't want."
Every time you think you know how nasty the world is, it just gets a little bit worse. =\