Not far away, Oracle CEO Larry Ellison is building a $40 million-plus replica of the Japanese Katsura palace on 23 wooded acres. Presumably, he'll be parking his new Marchetti Italian jet fighter elsewhere - perhaps next to the aerobatic plane he just bought as an eighth-grade graduation gift for his son. In Atherton, Tom Proulx, a co-founder of Intuit, recently bought three neighboring lots so he could build a 9-hole golf course in his backyard. One Woodside programmer bought 24 acres just to land his helicopter. "Keeping up with the neighbors in Silicon Valley is getting weird," says Daniel Case III, president and CEO of Humbrecht & Quist, Inc., It's not, "do your kids go to private school." It's "do they have a private jet?"