When one does a "make install DESTDIR=somedir" without having glade3 installed, the result is:
$ ls -al somedir
total 28
drwxr-xr-x  7 mj users 4096 2006-12-29 13:57 ./
drwxr-xr-x  4 mj users 4096 2006-12-29 13:29 ../
drwxr-xr-x  2 mj users 4096 2006-12-29 13:57 16x16/
drwxr-xr-x  2 mj users 4096 2006-12-29 13:57 22x22/
drwxr-xr-x  3 mj users 4096 2006-12-29 13:57 etc/
drwxr-xr-x  2 mj users 4096 2006-12-29 13:57 install/
drwxr-xr-x  7 mj users 4096 2006-12-29 13:57 usr/

The 16x16 and 22x22 directories look like pixmaps for use with glade3.  However, GLADE3_PIXMAP_DIR is empty (correctly as I don't have glade3 installed).  Without glade3, these two directories probably should not be created without glade3 installed and certainly should not be in the somedir passed as DESTDIR to make install.

The file libgnomedb-2.99.2/data/Makefile.am has:
SUBDIRS = 16x16 22x22

Thus, its subdirectories do not depend upon whether or not glade3 is installed.  They are always built and installed.  However, the file libgnomedb-2.99.2/data/16x16/Makefile.am has:
smalliconsdir = @GLADE3_PIXMAP_DIR@/16x16

Since glade3 is not installed @GLADE3_PIXMAP_DIR@ evaluated to an empty string and the 16x16 directory was installed incorrectly in the root of my DESTDIR.