Facebook (META -0.29%) went public to an enormous amount of investor excitement, but has since proven it was overvalued at that initial price, and has fallen substantially. Now that share price has stabilized, however, investors are wondering if the stock has reached a more reasonable valuation, and if it is a buy today. In this video, Motley Fool tech analyst Andrew Tonner discusses some of the challenges that Facebook faces today. Andrew addresses the key metrics investors are going to want to watch, such as its ability to monetize the current explosion in mobile Facebook use, and its further growth in some of the world's emerging markets.