BBDO Worldwide in New York, General Electric’s longtime advertising agency, was not getting the message. The agency had been offering G.E. its panoply of traditional marketing ideas, leaning heavily on the standard 30-second television spot. But Judy Hu, general manager for global advertising and branding at G.E., demanded something daring. What she eventually got fit the bill: an online campaign with a virtual sprouting seed that computer users can tend and send to people they know by e-mail.