When 12 Maryland dream homes burned to the ground and dozens more smoldered in an eight-hour blaze, the first thought on most people's minds was ecoterrorism. The luxury homes, uninhabited but worth roughly half a million each, encroached on one of the nation's last undisturbed magnolia tree bogs. Then another possible motive surfaced. Many of the homes had been purchased by African-Americans, and there were sightings of racist graffiti. "But it's our investigators who spray paint the homes as markers," Deputy State Fire Marshal W. Faron Taylor said. "I hope we've eliminated that rumor." At the weekend, investigators were questioning a security guard who had mysteriously left his post an hour before the blaze began.