Plugging my blackberry into a usb port of a generic ubuntu machine shows it's microsd card as something I can mount and everything works. Here's what happens when I try to do the same thing in raspbian:
raspberrypi$ find /dev > /tmp/without_bb
raspberrypi$ find /dev > /tmp/with_bb
raspberrypi$ diff /tmp/without_bb /tmp/with_bb
1a2,3
> /dev/sda
> /dev/usbdev1.14
18a21,22
> /dev/disk/by-path
> /dev/disk/by-path/platform-bcm2708_usb-usb-0:1.3.4.1:1.1-scsi-0:0:0:0
22a27
> /dev/disk/by-id/usb-RIM_Blackberry_SD_EB38692999EF1D8A3FD3AB10ED202905678036E1-0:0
26a32
> /dev/block/8:0
54a61
> /dev/char/189:13
205a213
> /dev/bus/usb/001/014
raspberrypi$ sudo mount -t vfat /dev/sda /media/blackberry
mount: no medium found on /dev/sda
raspberrypi$ file /dev/sda
/dev/sda: sticky block special
raspberrypi$