File sizes greyed out (strange extended attributes) in Finder on Lion?

Question

I just got a new machine with Lion preinstalled. After transferring all my applications, I noticed that the file sizes (and only the sizes) of some applications and folders are greyed out:

Does anybody know what this means?

Update:

ls -la gives the following lines for DjView and Dropbox:

drwxr-xr-x   3 daniel  staff    102 31 Okt  2007 DjView.app
drwxr-xr-x@  3 daniel  staff    102  3 Mai 10:06 Dropbox.app

I.e. Dropbox.app has extended file attributes, namely

$ xattr -p com.apple.FinderInfo Dropbox.app/
00 00 00 00 00 00 00 00 00 00 FF FF FF FF 00 00
00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00

Cheers

MrMage