This is the craziest part: first I tried copying iPhoto to an external hard drive, attached via USB. It said the process has been completed, but it wouldn't let me eject the drive. I Force Ejected it, and when I plugged it back in, the app wasn't there. Weird.
Then I tried dumping iPhoto to a 4GB USB stick, and... it fried the stick. It said it couldn't complete the operation and the drive disappeared. When I reattached it, OS X couldn't read it, nor could it fix it. I'm kind of blown away by this. Is it some form of DRM?
Finally I placed it on an internal drive that is not my main drive, but only used for archiving files. It copied there successfully, but it's an internal drive so I haven't tried removing it. I supposed I could unmount it, but am loathe to do anything that might make the drive useless.
Kind of an odd headscratcher here.