Avid users of iPhoto who also count their megs and gigs typically notice that the darling iLife app can quickly gobble up a good chunk of the hard drive. One practice that is sure to help inflate the size of your library is editing images. As it turns out, whenever you make edits and save, iPhoto duplicates the image, creating a backup; hence the usefulness of that 'Revert to Original' option. One problem with this system is that all these duplicates can pile up fast if you're an avid iPhoto editor - but thanks to some simple instructions in this MacRumors forum thread, you can put iPhoto on a diet. If you don't want to read through all the posts, Adriaan Tijsseling, the developer of ecto, endo and 1001 (an excellent Flickr client), has whittled out the meat to help get you on your way. Adriaan's post contains the simple commands to run in Terminal (along with an explanation of what is going on) that will effectively remove all the original copies of any images you have edited in iPhoto. While this obviously means you'll lose the ability to use that 'Revert' option (in case you try it, you won't break iPhoto; it's just that nothing happens), this could be a useful trick for anyone trying to reclaim every last byte of free space.