This may seem like a silly question, but I never really thought about it until now. What do people do who have large sums of money (millionaires and billionaires) in cash? FDIC only insures up to 100 G's. Do they put it in 10 different banks? Surely they don't invest all of it.

Don't know, bud. Read the new much? FDIC is up to $250k, and that is per account, i.e. individual, joint, individual w/POD, etc. not per bank. Check out the EDIE tool on FDIC's site for more info on that, chief. Peace...

Most people with huge amounts of money (is anyone left ;) ), invest their money in various instruments. It could be stocks, bonds, real estate or various other types of investments. Very few leave a lot of cash lying around, whether in paper or bank accounts.

There are special programs that insure lots more money, but you have to be aware of it, and put your money in the specific banks that use them.