(Markets Edition) As you may have already heard, the GOP tax plan may cap the annual amount you can contribute to your 401(k). And that'll mean Republicans could start pushing for the expansion of Roth IRAs, where you opt to be taxed now, not later. Marketplace contributor Chris Farrell stopped by to explain the flaws in our current retirement-savings system, and why these new changes could just end up making things worse. Afterwards, we'll look at the blurry ways of classifying Google, Twitter and Facebook. Should they be considered newspapers, publishers, or just platforms for information? And finally, we'll discuss Facebook's (very successful) business model, and the value of its return on investment for advertisers.