Tumblr had a strong 2012, reaching 170 million monthly users and cracking a global list of the highest-traffic websites, but the next 12 months could bring big changes as it seeks to monetize through advertising, to reach new audiences and to demonstrate its value while focusing on content and shared interests rather than user interactions, Ingrid Lunden writes. "[I]f sites like Facebook and Twitter are focused on increasing engagement, then Tumblr has a shot at carving out a different kind of business path," Lunden writes.