user permission for gvfs

UsbSticks are automatically mounted by gvfs for the user who has the
gnome-session. The mountpoint is created just for this and removed afterwards.
Even an icon appears on the desktop. All this is exactly what I want.

But I have another user logged on, who wants to r/w the UsbStick too. The
permissions are too restrictive though. The second user isn't allowed anything.

Where can I change that???!!!

(To define everything in fstab would be an option, but a bad one because
I would have to keep a whole bunch of possible mountpoints in /media.)