"He's been asking me for weeks to get him a Nintendo DSi for Christmas," Alicia explained. Her son, Alex, is only nine. Christmas is well over a month away but he's been relentlessly pressing for the "must-have" electronic toy that his classmates already own. Money is tight for Alicia's family these days, and the handheld device starts at 149.99. Games are extra, at $35 a pop. Alicia doesn't indulge in expensive clothes, trendy bags, or "must have" purchases-at least for herself. But when it comes to her son, mom-guilt too easily clouds her perspective. And retailers and advertising gurus wouldn't...