Magnetic Threats
Some of the more subtle sources of magnetism include:
Computer Monitor
Don't put floppy disks anywhere near the monitor; it generates a magnetic field.
Telephone
When ringing, telephones (particularly older phones with a bell) generate a magnetic field.
Bottom Desk Drawer
While the desk drawer does not generate a magnetic field, the vacuum cleaner that the maintenance people slide under the desk to clean the floor does.
Bottom Bookcase Shelf and File Cabinet Drawer
Same comment as the desk drawer just above.
Pets
Pet fur generates a strong electrostatic charge which, if discharged through a disk, can affect files on the disk. Instead of "The dog ate my homework," today it could just as easily be: "The cat sat on my homework."