When mounting a virtual file system using GVFS it can be easily accessed using Nautilus. However, when I use most of my GTK based applications (i.e. Firefox or VLC), the virtual file systems are not shown in the "Open file" or "Save file" dialogs.
These file systems can be still accessed from the .gvfs folder, but as I understand, this folder is ment to support command line or non-GTK applications, and my problem exists with GTK applications. Accessing these file systems through .gvfs is less comfortable and less intuitive.
Is this a bug, misconfiguration or a feature by design?

I am using Ubuntu 10.04.03 LTS