Retailers trying to woo shoppers with early deals and longer hours this week, and throughout the holiday season, could be putting their profits at risk as shoppers search for bargains and not much else. Wal-Mart Stores Inc, Toys R Us and outlet malls are among those hoping that big discounts on Thursday night will attract shoppers hungry for deals after Thanksgiving meals. Others such as Target Corp, Macy's Inc and Kohl's Corp will join the fray during the wee hours of Friday, opening their doors hours earlier than in past years. The early sales, along with more advertising spending, show that retailers are taking no chances as they fight for their share of the limited amount shoppers plan to spend. The moves, which include adding staff, securing bargains on video games and offering free shipping, also can eat into profit margins. Gross margins at U.S. department stores and broadline chains are expected to fall an average of 0.4 percentage points this year because...