Business
It seems that Apple's automatic backup utility, Time Machine, doesn't back up iPhoto libraries when iPhoto is running. That's not so good for the whole "back up" concept.
A recent support document warns about this behavior and suggests that users quit iPhoto before Time Machine does its thing. Or you can quit iPhoto and force a back up with the Back Up Now command from the Time Machine menu.
I admit that I am a bit paranoid about this backup and at the end of the day, I quit all applications and click the Back Up Now command. This may be magical thinking but it has given me a bit of extra peace of mind. And now, this support note supports my thinking.