If your distributions does not allow your users to mount storage device ( i.e. usb memory ) and it appears that you are using Gnome 2.14 ( and maybe higher ) and you wish to actually allow your self this pleasure :

Under gentoo :

1. your user should be in plugdev group.
2. /media directory should exist.
3. And after you have added your self, log out, and in again.
4. Restart dbus!

The fourth step came to me after reading gnome-mount -vt output. It was around 30 minutes of googling, completely useless.