CAMBRIDGE, MASS. — John Lester, Boston operations director for Linden Lab, the maker of Second Life, is giving the standard sales pitch for the virtual world. His claim: "It's full of people." We wonder if Lester (pictured) would so readily say that to Second Life's corporate-marketer customers, who have found their 3-D Second Life "islands" to be virtual ghost towns. Or to Second Life's disgruntled users, who are stymied by the service's struggle to increase its population capacity. "Our brains crave it," Lester claims. His former job? Creating online communities for patients with neurological disorders. That speaks volumes about Second Life's user base, doesn't it?