BART has been slowly increasing its in-train advertising. We're currently at late-80's Candlestick Park levels of billboards, the era before they actually had GAP ads on the playing field. I expect that BART's Poetry In Motion series will be replaced by ads for housing developments or the United Association of Plumbers and Pipefitters in the next year or so, moving them closer to mid-90's Candlestick Park-era selling out.
Where BART is limited, compared to money machines like professional sports stadiums, is the naming rights. The Giants can sell the name of their stadium, and change it every three years, and no one really gives a damn. Banks and telecommunications companies buy and sell one another, power companies go bankrupt, cable operators fall apart due to internal corruption, but teams don't really care as long as someone is signing a check.
BART doesn't have a main facility like a sports team does. The station names are dictated by geography. However, I do think that BART could sell the naming rights to the individual lines. The geography doesn't matter as much there. It's not like anyone ever goes to Fremont anyway.
My first suggestion? Get KTVU to pony up some dough to make the north-bound East Bay line into the Dennis Richmond Line. The ratings for the Ten O'Clock News will skyrocket. KPIX won't know what hit them.
The opportunities for cross-promotion are endless. Leslie Griffith's face adorning tips for avoiding terrorism at Lake Merritt. Brian Banmiller reporting on business from El Cerrito Plaza. And every Sunday, on one lucky train, Fred Inglis walks through all the cars without any pants on.