Most of the TV-watching public in the United States probably knows the jingle already: If you have a structured settlement and you need cash now, call J.G. Wentworth (877-CASH-NOW). However, this is pretty much always a horrible idea, according to the reporting and research John Oliver presents about J.G. Wentworth and other factoring companies on this week’s Last Week Tonight. In short, these companies are going to take the vast majority of tha…