Regulators on Friday shut down two big California banks, as well as banks in Alabama, Florida, Georgia, Michigan and Illinois, bringing to 140 the number of U.S. banks brought down this year by the weak economy and mounting loan defaults. The Federal Deposit Insurance Corp. took over all seven. Regulators shuttered First Federal Bank of California, based in Santa Monica, with $6.1 billion in assets and $4.5 billion in deposits, and Imperial Capital Bank of La Jolla, Calif., with about $4 billion in assets and $2.8 billion in deposits.