As the pads wear the piston moves in on the caliper and in turn the brake fluid fills the space the piston took up. That lowers the level in the brake fluid tank. There is a float in the tank with a reed switch. When the level gets low it makes the light come on or sometimes just flickers when you make turns or accelerate because the fluid is sloshing around. Scoobies seem to be sensitive to the level bring fluid to the MAX level and the light will go out. It's never a good idea just to add fluid and go on your merry way when the light goes out. You need to check and see why it went low. More often than not it's just the pads wearing like normal. But it could be a leak so it's worth having a look at each wheel for fluid an inspection the brakes which it sounds like you did. I have info here:
2010 Legacy 3.6R (Mine) 2013 Outback Premium (Wifes)
2001 Outback (Son), 2001 Forester S (Daughter)
1999 Miata (my summer ride)
Last edited by Peaty; 04-30-2012 at 08:25 AM..