Canadians are using credit cards to pay for purchases more than ever before.Why wouldn't they? Cash has been on the decline and rewards programs are better than ever. But small businesses say these programs are killing them, and it has become almost impossible to understand the complex system of fees that go into these payments. Right now, Ottawa is asking card companies and retailers to come to an agreement, before it has to step in and regulate. But why? How does the system work? Who pays for what? And what do you need to know the next time you whip out a card and chase the points during your holiday shopping?GUEST: Susan Krashinsky Robertson covers the retail industry for the Globe and Mail's Report on Business