This week I've started planning for the next version of our data collection system. The key realization for me is that I do not know all the questions we will need to answer in the future. Our current focus is on specific sequences of click events, but in the future we might want to look at browser versions or behavioral patterns related to IP addresses. If we don't capture user-agent, for example, we won't be able to answer questions about browser versions. If we don't capture IP then we cannot look for patterns in IP addresses. We should store data in a way that maximizes the range of questions we can address in the future. In the past few years, the cost of storing data have continued to fall. We use AWS extensively. Amazon S3 costs are very reasonable and guarantees a high level of availability. Also, lower compute costs and open source tools like Hadoop that process large data volumes have greatly increased our ability to extract valuable insights from data. So s