Twitter (TWTR) has been down in the dumps lately, with shares suffering year-to-date losses of over 50%. Most of that pessimism has related to user growth, which has significantly slowed over the past few quarters. Twitter has hit a ceiling in the U.S., its most important market. That's why the company will need to focus on international growth going forward.

eMarketer predicts that Twitter will approach 400 million monthly active users by the end of 2018, which represents significant upside to one of Twitter's most important metrics. However, the deeper challenge lies in monetization. International users represent nearly 80% of total users, but contribute just under 30% of total revenue. There are a lot of costs associated with international expansion, including growing a sales force and building up network infrastructure, and Twitter will need to make sure those investments pay off.

LinkedIn (LNKD.DL) has much more promising prospects with international growth. Its registered member base is comparable to Twitter's, but it has far more opportunities in key markets like China where it is expanding.

In this segment of Tech Teardown, Erin Kennedy discusses Twitter's future with Evan Niu, CFA, our tech and telecom bureau chief.