Walmart has signed an exclusive deal with Henkel to put Persil laundry product on store shelves. Analysts note the move could hurt sales of Procter & Gamble's Tide laundry detergent. P&G holds 60% of the US detergent market and 85% of profits, according to analysts, who have suggested that Walmart made the move after P&G reduced the amount of detergent in some of its containers last year....