It’s a misconception that you need to know who a user is to improve the relevancy of the individual user. How did they find your website? We don’t need to know the name, address and Facebook friends to personalize content to our users. When working with personalization you can start out with as little data as single click on your website. Or you might be able to detect whether the user has visited your website before. What did they show interest in?
Sometimes the data isn’t specific to the user at all. Sometimes it describes a huge set of users. Often you can retrieve real gold in looking into your business intelligence. This could be data about churn, successful cross-selling strategies or other behavioral metrics.
Sometimes the most valuable piece of information is whether the user previously has signed up to a newsletter – simply because it indicates a level of interest.
Using Sitecores rules editor you can setup a lot of rules, without being able to uniquely identifying the user. Time of day, triggered goals, visited pages and so forth can help you display information with higher relevancy.
Sure, the more data the merrier, but don’t let the lack of specific user data stop you from trying to elevate the relevancy of your website to the individual user.