A new Apple knowledgebase article effectively says, keep things where you found them: iLife ’06: Don’t move iLife support files from installed locations. This is one of the tradeoffs that make iLife easy to work with. As long as you’re happy with where Apple stores your files, you won’t have problems.
I guess this is a sideways opportunity for me to complain about iDVD’s insistence on putting project files in my Documents folder (instead of the working partition that I use that has more disk space). After creating an iDVD project from within iMovie, iDVD should launch and ask where I would like the iDVD project to live. Instead, I forget that it’s in my Documents folder (in my home directory), until I suddenly realize that I have no free space on my startup disk.
Okay, mini-rant over. I feel better.