Surely it's not a Hack as such?
Guessing a "secret question"...heck in fact someone having what would be a considered a fairly important public facing feed with a security question that can be guessed by someone who's first language isn't even the same is pretty poor to start with..but then a twitter feed's hardly going to start wwIII or divulge state secrets now is it?
"Obama lost his mobile - could world leaders please call him on the new cell at xxxxxxxxxx"
"Obama things china should suck his chocolate salty ones, what you gonna do about it!*
"China declared war on USA."