A fast-moving brush fire driven by 50- to 70-mph winds erupted Thursday night in the hills above Montecito in Santa Barbara County, burning at least 800 acres, destroying up to 80 homes and forcing evacuations of luxury neighborhoods, authorities said. The fire broke out about 6 p.m. in the wealthy Cold Springs area of Montecito, where a number of celebrities live, and quickly overwhelmed firefighters with its speed.