So, I open up projects to disk, open.. a project, one within that, 
and another within that, and enter the project.

I drop a few morphs, go up to the parent project, drop a few morphs, 
and continue all the way to the top.  Save the image.

Go in again and visit the projects, mess with the morphs for awhile, 
save again.

Now, I go in again and systematically delete the test projects, 
deepest first all the way back to the top.  (Aside:  Should there be 
a facility for deleting projects that also contain projects, albeit 
with a "is that really what you want" message?)  Save again.

Lo and behold, the project segments remain in the image_segs folder, 
and aggregately took up a non-trivial amount of space.  Is this 
intended, or are these guys eventually collected by some other means?

I even do a garbageCollect for good measure.  Save again.  Spore remains.