Sorry if this is a stupid question, but I'm trying to help out a friend with her first digital P&S. I've dealt basically with Canon and CF cards.

Do all cards/memory sticks, etc. have to be formatted before use and reformatted periodically? Michelle has a Panasonic that uses an SD card.

Also (question for me also). How often do cards need to be reformatted? Can images be left on them without reformatting indefinitely?

What happens if you don't format and/or reformat periodically?

Thanks for any information.

Liz