Bill Me Later's surprising successSAmazon.com has taken a minority stake in Bill Me Later, according to reports. Why? Likely, it has something to do with the 217 percent year-over-year increase in traffic to BillMeLater.com, where users sign up for new accounts. As part of the deal, Amazon will join Wal-Mart and Overstock.com in adding Bill Me Later as an online payment option.