Several socio-economic trends are driving customer demands towards individualization. Many suppliers are responding by offering supplier-led software product design customization choices (“mass customization”). Some are also offering customer-led software product design choices (“mass personalization”). This tutorial introduces these concepts and explores the implications for software product line development. One particular technical challenge is being able to respond to and manage at scale the increasing variety of common, supplier-led and customer-led features. We will discuss two different approaches to address this challenge. One is grounded in feature modelling, the other in case-based reasoning, where the latter relies on measuring similarities. We will then describe a specific product similarity evaluation process in which a product configured from a product line feature model is represented as a weighted binary string, the overall similarity between products is compared using a binary string metric, and the significance of individual feature combinations for product similarity can be explored by modifying the weights. We will illustrate our ideas with mobile phone worked examples, and discuss some of the benefits and limitations of this approach.