Daniel Tunkelang discusses three key areas - relevance, recommendations, and reputation - that LinkedIn is focusing on to improve the user experience. Relevance refers to improving search and discovery of profiles by combining different types of signals. Recommendations match members to jobs, groups, and other connections. Reputation involves identifying member expertise in skills and who the experts are in particular skills. Open problems remain around exploratory search, balancing exploration and exploitation of the data, and incentivizing the development of online reputation.