Our personal bank accounts here in America are now insured up to $250,000. But say you won $250,000,000 in the Powerball or something. That's 1000 seperate bank accounts to make sure all your money is safe.
You tool. You're insured for a maximum of $250k at separate BANKS, not in separate accounts. Otherwise everyone would do what you're describing and the FDIC wouldn't work. Good luck finding 1,000 different banks - and dealing with the hell of having to deposit $250k in each of them!
You have two OTHER options:
a) put all $250m in the same account, because this isn't the great depression and banks don't fail anymore (and those which do fail, like Wachovia, are bought up by other banks and continue to operate normally).
b) invest the $250m. Even in an index fund. This is probably safer than banks because even with the recent market volatility, time has proven the market is an extremely safe investment if you hold steady for the long term. Plus it keeps your asset relatively liquid (vs., for example, real estate, or art, or some other investment), since you can pull out with relative ease and no penalty.
There's also rarely-utilized option C, wherein you could open a Certificate of Deposit (CD) with the money and earn better interest than a savings account. The positive here is that the FDIC insures CDs up to $50m, but the negative is that CDs are long-term lock-ins so the money is completely illiquid.
If I had $250m and wanted to keep it as a nest egg as best as possible, I'd probably do a $50m CD for the shortest term possible, put about $10m in a simple savings account, and keep the rest in very low-risk stocks. You have almost no chance to lose everything there, and you're diversified enough so that if one of your stores of money fails, you're still holding good money in another. Then again if you had $190m in an index fund and the market failed, the last thing I'd be worrying about is my remaining $60m. I'd be more worried about the impeding nuclear war.
1,000 separate accounts. What a dumbass.
(BTW there are literally TONS of other options you could do as well... I believe some offshore banks have no insurance limit)