'find' nogroup/nouser doesn't traverse directories?

flamingo:~ joliver$ sudo find / -nogroup
find: /dev/fd/4: No such file or directory
find: /home: No such file or directory
find: /Library: No such file or directory
find: /net: No such file or directory
find: /Network: No such file or directory
find: /private: No such file or directory
find: /sbin: No such file or directory
find: /System: No such file or directory
find: /Users: No such file or directory
find: /usr: No such file or directory
find: /Volumes: No such file or directory
flamingo:~ joliver$ ls -l /
total 30453
drwxrwxr-x+ 40 root  admin      1360 Oct 23 16:01 Applications
drwxr-xr-x+ 66 root  wheel      2244 Oct 12 15:01 Library
drwxr-xr-x@  2 root  wheel        68 Jun 18  2011 Network
drwxr-xr-x+  4 root  wheel       136 Oct  1 14:08 System
drwxr-xr-x   7 root  admin       238 Oct 12 10:19 Users
drwxrwxrwt@  4 root  admin       136 Oct 26 14:16 Volumes
drwxr-xr-x@ 39 root  wheel      1326 Oct  1 14:01 bin
drwxrwxr-t@  2 root  admin        68 Jun 18  2011 cores
dr-xr-xr-x   3 root  wheel      4250 Oct 26 13:30 dev
lrwxr-xr-x@  1 root  wheel        11 Oct  1 12:52 etc -> private/etc
dr-xr-xr-x   2 root  wheel         1 Oct 26 13:46 home
-rw-r--r--@  1 root  wheel  15572704 Aug 23 16:27 mach_kernel
dr-xr-xr-x   2 root  wheel         1 Oct 26 13:46 net
drwxr-xr-x@  6 root  wheel       204 Oct  1 12:57 private
drwxr-xr-x@ 62 root  wheel      2108 Oct  1 14:01 sbin
lrwxr-xr-x@  1 root  wheel        11 Oct  1 12:52 tmp -> private/tmp
drwxr-xr-x@ 12 root  wheel       408 Oct 15 08:22 usr
lrwxr-xr-x@  1 root  wheel        11 Oct  1 12:52 var -> private/var

flamingo:~ joliver$ sudo find /Library -nogroup
/Library/McAfee/abm
/Library/McAfee/abm/bin
/Library/McAfee/abm/bin/abm
/Library/McAfee/abm/lib
/Library/McAfee/abm/lib/libABMCommon-3.5.0.1.0.0.dylib
/Library/McAfee/abm/lib/libABMCommon-3.5.0.1.dylib
/Library/McAfee/abm/lib/libABMCommon.dylib
/Library/McAfee/abm/lib/libABMCommon.la
/Library/McAfee/abm/lib/libABMEngine-1.0.0.1.0.0.dylib
/Library/McAfee/abm/lib/libABMEngine-1.0.0.1.dylib
/Library/McAfee/abm/lib/libABMEngine.dylib
/Library/McAfee/abm/lib/libABMEngine.la
/Library/McAfee/abm/lib/libABMPlugin-3.5.0.1.0.0.dylib
/Library/McAfee/abm/lib/libABMPlugin-3.5.0.1.dylib
/Library/McAfee/abm/lib/libABMPlugin.dylib
/Library/McAfee/abm/lib/libABMPlugin.la
/Library/McAfee/abm/lib/libboost_date_time.dylib
/Library/McAfee/abm/lib/libboost_filesystem.dylib
/Library/McAfee/abm/lib/libboost_program_options.dylib
/Library/McAfee/abm/lib/libboost_regex.dylib
/Library/McAfee/abm/lib/libboost_system.dylib
/Library/McAfee/abm/lib/libsqlite3.0.8.6.dylib
/Library/McAfee/abm/lib/libsqlite3.0.dylib
/Library/McAfee/abm/lib/libsqlite3.dylib
/Library/McAfee/abm/lib/libsqlite3.la