The Consumer Financial Protection Bureau launched its first big initiative Wednesday, announcing that it would look into the overdraft fees that banks charge their customers, a practice worth billions of dollars. The inquiry is to investigate the fees that an economic research firm, Moeb $ervices, say amount in up to $38 billion in revenue for banks in 2011. Banks charge up to $35 for each overdraft, enabling customers to overdraft but slapping a fee that, the firm said, is most hurtful to low-income individuals. A 2008 study found that 46 percent of young-adult account holders incurred overdraft charges. The CFPB is said to be seeking out a “penalty fee box” for customers’ account statements that would detail the total costs incurred due to overdrafts.