How much does an LCD's backlight drain the battery? The screen tends to be one of the biggest consumers of electricity. How much of this is for the backlight vs the actual screen, particularly in the case of an LCD?
Not only the screen is a main consumer. Based on the Motorola Droid, I can give you some data to compare:

Video recording         1557 mW
UMTS Upload             1410 mW
UMTS Download           1349 mW
EGDE Upload             1179 mW
WLAN Download           1158 mW
Video play (fullscreen) 1135 mW (already minus the display)
UMTS phone call          983 mW
Camera                   934 mW
EGDE Download            853 mW
Bluetooth receive        751 mW
Display (at max)         730 mW
GPS Search               550 mW
GSM phone call           511 mW
Bluetooth send           487 mW
WLAN Upload              479 mW
Display (at min)         310 mW
MP3 play                 160 mW
UMTS Standby              18,3 mW
GSM/EDGE Standby          11,6 mW
WLAN Standby               7,8 mW
Bluetooth Standby          2,8 mW
GPS Standby                0,4 mW


As you can see, there are clearly compontents/actions with a much higher energy consumptions -- but the display gives you good potential to reserve some.

Data source is an article at Heise.DE called Energiesparplan (google translate version here).