If you're sharing photos over your network, disable that here
Connect to shared photo libraries over the a network
A run down of the iPhoto Preferences
Enable or disable copying photos into the iPhoto library when you import photos
Change the background appearance for iPhoto
Change the text size in iPhoto
Change what happens when you plug in a digital camera to your computer
Choose to edit a photo in an external program, in a separate window, in full screen, or in the main window
Change what program iPhoto will use to email photos with
See how many photos and videos are in each event or library right from the album/event pane
Share photos over your network, other computer users and Apple TV users can connect
