They may not be blood brothers, but Paul G. Allen, the cofounder of Microsoft, and Larry J. Ellison, the CEO of Oracle Corp, the world's second largest software company, are the Cain and Abel of the silicon set. Their rivalry knows no bounds. They compete with the same intensity as the characters in the Jeffery Archer novel, at every level in business, sport and pleasure-particularly in the yachts they own. Lastly, and most ironically for two titans whose head-butting contests have raised such a heavy wake, both men are obsessed with secrecy.

When Allen ordered his latest superyacht, the 416-foot Octopus from the Lürsson yard in Germany, Ellison was soon to follow with an order for the monster 452-foot Rising Sun, which became the second-largest private yacht when he had the hull extended from 387 feet during construction. Naturally some amateur psychologists say the extension was done simply to steal Allen's thunder.

If so, lightning may have struck twice, from an unexpected quarter. Rising Sun was launched from the same German yard as Octopus last autumn, but surprisingly, Ellison, a dropout from the University of Illinois, has yet to accept delivery-the sort of pouty ploy practiced by billionaires who've learned to throw their weight around. The latest word suggests that he has now lost interest in her since the $270 million vessel has been superseded in the size league by the 525-foot Platinum, launched for engine trials in April and currently being completed in Dubai for Sheikh Mohammed bin Rashid Al Maktoum. The Crown Prince of Dubai makes a most worthy foil, being the owner of the Emirates airline-which just placed a $28 billion order for the new Airbus.