The icon -- which Twitter users call it the "fail whale" because the creature appears only when the site has failed to load -- has gained a cult following as the social media site grows at breakneck pace. The conversational Web site, which lets users post 140-character microblogs, saw a 1,374 percent jump in unique visitors between February 2008 and February this year, up to 7 million from only 475,000, according to Nielsen NetView. By comparison, Facebook grew 228 percent, to 65.7 million users, during the same period. - Adriana