When my father died 4 years ago all of my mothers bank accounts, credit cards etc. were locked because his name was on everything. They find out you die and shut everything down. I'm not sure who tells them but they do find out within a few days of your death.
It turned out that my father didn't sign anything on all the joint accounts except the house mortage so all her accounts were unlocked pretty fast once she told them. He didn't like to sign anything concerning credit because he was just a little old school and believed in cash. He even had a blank check in his wallet when he died that was over 10 years old-he never used it.
The funeral home wouldn't take a check with his name on it as well. The funny thing now is their phone still comes over the caller ID in his name so I guess AT&T doesn't know he's dead yet :)
Once in the computer you never get out.