Description:It's enough to get a Carnival shareholder seasick. The world's largest cruise operator warns of lower revenue and earnings amid a string of horrific mishaps at sea - two this week alone. Carnival says its net revenue yields will be flat this year instead of the 1 to 2 percent increase it had expected. It has been offering discounts to lure customers, especially in Europe. Morningstar analyst Jaime Katz:(2:11)