If you're trying to use iPhoto '09 on older pre-Intel hardware and/or if you have a very large photo library, you may have noticed that many face-related operations, such as tagging and drag-selecting, take an inordinate amount of time. During these delays, iPhoto may appear to be locked, or you may be treated to the wonderful spinning beachball cursor show while iPhoto thinks about what you've just asked it to do.
Short of ordering a eight-core Mac Pro with 32GB of RAM, I'm afraid I don't have an iron-clad solution to this problem. I do however, thanks to Mac OS X Hints contributors Chris Devers and Brian Hagemann, have a suggested fix that may reduce the delays.
When you look at your albums and libraries in the left-hand pane in iPhoto, do you see photo counts next to each one? While these little numbers may prove useful, they may also be somewhat responsible for the slowdowns you're experiencing. The task of updating these counts whenever you modify your images appears to cause iPhoto to slow down, at least for some users.
To disable the item counts, open iPhoto's preferences, and on the General tab, uncheck the 'Show item counts' box. (On my machine, toggling this checkbox sometimes seems to take a few seconds, so don't go click-crazy if it seems like it's not working.)
After disabling the photo counts, try tagging some faces and see if the slowdowns have disappeared--or at least been reduced to bearable levels. For both Chris and Brian, this simple change made a huge difference. On my Mac Pro with a 17,000ish photo library, the change isn't really noticeable. But if you're experiencing slowdowns in faces and use photo counts, it might be worth disabling them to see if it makes a difference.
This story, "Speed up IPhoto '09 Operations on Some Macs" was originally published by Macworld.